Back in November 2025, I wrote a review of the Space Marines Codex for Warhammer 40,000. Recently, I read the book again and was so excited by it that I felt compelled to write a review, completely forgetting that I'd already written and posted a review. This post is my second review of the Space Marines Codex for 10th edition Warhammer 40,000. Spoiler alert: It's still a great book.
As with other codexes, the first portion of the book consists of lore and background material, followed by army photographs and painting guides, and then by game rules.
Within the lore of the Warhammer 40,000 universe, the Emperor of Man establish 20 space marine legions. After the civil war that was the Horus Heresy, 9 loyalist legions remained. These 9 legions were divided into 9 space marine "chapters", from which countless derivative chapters formed.
I imagine it must be difficult to know what to include in a 10th edition codex. On the one hand, there have been about 9 codexes on this topic already. On the other hand, new people are being introduced to the game all the time, so to them everything in this codex is new information. There are people somewhere in between, too. I'm not entirely new to the Warhammer 40,000 universe but I'm pretty new (less and less as time goes on, obviously) to playing the tabletop game.
This codex strikes a great balance, I think. Keeping in mind that there's already been an introduction to space marines in the rulebook, this codex uses most of its lore section to explore the 9 original space marine chapters, and the meaning and placement of heraldry and rank markings.
If you've read a few Black Library novels, then you probably have a good idea of what makes each chapter unique. If you haven't, then this provides an excellent one-page overview about each one, plus the Black Templars. The inclusion of the Black Templars amongst the 9 founding chapters is a little puzzling to me. They're the only chapter that's not a founding chapter to be given its own page, and frankly I feel like it confuses the matter of chapter lineages. If you don't read very carefully, you might put the book down thinking that the Black Templars were a founding chapter.
After the one-page overviews, the codex provides an excellent explanation of the weaponry, the company structure, individual ranks, and even many of the unit types. It's a gold mine of information for anyone trying to understand how to structure an army for lore accuracy. If you enjoy flipping through documentation about historical armies, this is the codex for you.
Better still, the lore section dedicates 3 pages to derivative chapters, like the Crimson Fists from 1st edition Rogue Trader, the mysterious Mantis Warriors of the Badab War, the Sons of Medusa, Dragonspears, and many many more. This serves partly as a great resource for painting inspiration as well as fun paragraph-length lore about a chapter you might prefer to the 9 founding ones (and the Black Templars, for some reason). It also serves as a gentle but appreciated reminder that you don't have to paint your marines in any one specific way. You can invent your own chapter with its own paint scheme and its own ranking markers and heraldry. It's one of those things that you probably already know (there are no paint police), but it feels good to be reminded nevertheless.
Games Workshop has an uncanny ability to distill a seemingly complex process like painting into a regimented and simple process. Space marines are the exemplars. They can be painted in basically 3 steps.
Is that even 3 steps? It's nearly 2 steps, and it's no exaggeration. I've painted space marines, and it really is that simple.
The next section in the book is a featured combat patrol army list and ruleset. I say it every time I talk about Combat Patrol, but this is easily my favourite way to play 40k. I love how tidy the design is. Grab a few pre-defined units and associated data cards, and play. It's a great grab-and-go experience, a little like using pre-generated characters in a dnd game.
The combat patrol in the book, Strike Force Octavius, is a little quirky in that it uses an Infernus Squad armed with flamers as its core infantry. As an introductory army, that seems not very generic, and I can't help but feel that a unit of classic bolters would feel a lot more space marine-y. Aside from that though, the army is a good one and otherwise feels like a pretty classic line-up. There's a captain and a librarian, a unit of terminators, and a unit of space marines. Simple but broadly representative of the space marine model line.
The true power of Combat Patrol is that it doesn't have to be a model kit. Games Workshop can drum up Combat Patrol lists on paper and release them as downloads or as White Dwarf articles. That's exactly what they do, so the codex Combat Patrol list isn't the only space marine list out there.
More importantly, Combat Patrol serves as a good example of how to play a small 40k game. It gives you permission to ignore the whole 1000-2000-3000 point game sizes, and to just grab the models you have, put them on the table, and roll dice. That's how I think Warhammer 40,000 ought to be played.
The big army rule for Adeptus Astartes is the Oath of Moment. At the start of your Command Phase, you choose an enemy unit and then, for the duration of the round, you can re-roll Hit rolls against that unit. That's a nice broad rule for space marines, because in the lore all space marines, not just one or two chapters, practise the Oath of Moment.
The peculiar thing about space marines is that it's not really just one army. There are lots of chapters within the army, and they're all purported to be distinct. The space marine founding chapters of Warhammer 40,000 are:
To justify all those distinct chapters existing within what is, in the game, the same army, the lore gives each chapter a few specialties. The White Scars, for instance, are supposed to be famous for speed. It's a lot like different classes in an RPG, though. The lore asserts a specialty, but in practise you can run the army any way you want. If you have a bunch of marines on bikes, but you paint them as Ultramarines, then you've got an army that's just as speedy as White Scars. Alternatively, you could build a White Scars army without any bikes at all and they'd be no faster than any other chapter. Salamanders are known for flamers, but you can build any army with flamers (for example, Strike Force Octavius) and you end up with the same result. In other words, this codex provides no special benefit for any specific chapter.
I feel like this is a missed opportunity. If you're going to create 9 chapters of marines and write lore that makes them highly distinctive, then you may as well back it up with rules. The perfect vehicle for this are detachments, which exist as part of 10th edition anyway. Why not write a detachment for each founding chapter, and maybe one generic detachment for people running custom chapters?
The detachments in the book are good, though. There's a generic one that'll broadly work for any space marine army. After that, there are several those that hint at specific chapters in everything but name.
For whatever reason, the codex stops short of mapping a detachment to each founding chapter. I'm guessing that any founding chapter that doesn't get a detachment here is scheduled to get a codex of its own, with the exception of the Ultramarines, which I think are truly the all-purpose chapter. It's not by any means detrimental. Fact is, you can build your army as either a founding chapter, or any other chapter, and select whatever detachment matches your build or play style. There are several to choose from, so chances are you'll find something you like.
After the detachments, you get the data cards you need to play a gamewith your space marine army. Some (but not all) chapters do have their own codex, so this is very much a catch-all collection of profiles. For the most part, that's fine. Unless you play, for instance, Blood Angels. You won't find data cards for the Sanguinary Guard in this book, because those are exclusive to Blood Angels. If you paint your space marines red and call them Blood Angels though, you can play them using these rules. It only "breaks" when you get a unit that happens to be too specific to a given chapter. I don't know how you can tell in advance, so I can imagine buying a model kit and a space marine book only to later realise that you needed a special codex for that model kit. The lack of a hard connection between models sold by Games Workshop and the rules sold by Games Workshop continues to mystify me.
The final section in the book is dedicated to Crusade rules, which is an add-on system for playing a campaign. I play mostly campaigns, so I'll probably end up using this section eventually. I love a good campaign, because I love watching an army level up RPG-style. For me, this is best expressed by the Battle Traits subsystem, which allows you to earn experience points (XP) for battles and achievements. You can spend XP on bonuses (+1 to Hit, or +2 to speed, and things like that) for your units.
There's a lot more available in the Crusade rules than just Battle Traits. There's a system for requisitioning more firepower into your Crusade list, and Honour Points for increasing your ranking as you collect victories, and agendas and secondary agendas. I don't currently bother tracking those in my games because it's a lot of maintenance between games, and frankly I prefer to focus on the narrative aspect of a campaign between games.
If there's a critique to be had for the Crusade system, it's definitely the lack of narrative. I don't think there's room for a narrative in the Crusade rules, but I played through every mission in the Pariah Nexus and despite there being 80 pages of excellent lore, the missions were disjointed and narratively stagnant. That's not Crusade's fault, but if you're going to play Crusade then be prepared to fill a lot of missing story in for yourself.
What Crusade doesn't lack is flavour. The Battle Traits are highly specific to major unit types, which I guess technically limits choices but the choices you do have feel spot on. Even better are the relics, including the Relic of the Primarch, which can be dropped (should you lose the model carrying it) so it can be potentially retrieved. If you can go through that without coming to actually believing you own a priceless relic, then you're officially a boring adult, and you need to stop playing games.
This is easily one of my favourite 10th edition codexes I've read so far. This one's packed with informative lore, useful fictional military history and specifications, and lots of fun rules to bring to the table.
It's not organised exactly the way I'd have done it myself. One detachment for each founding chapter just seems obvious to me. But that's an untested opinion, and I'm not even sure I'd defend it if somebody who did actual market research and playtesting took me to task on it. It could be that "flattening" the chapters makes it easier for players to decide what chapter they want to buy into. After all, it's not useful for you to feel that you can never use a flamer unless you paint your toy soldiers green. That's silly, obviously, so maybe allowing chapters to be distinct in lore but basically the same in rules is the smart and player-friendly solution.
My standard disclaimer for Warhammer 40,000 (and to be fair, most tabletop RPGs) is that there are technically too many rules. However, the design of 40k is increasingly modular, so there's a lot in the codex you can blissfully ignore. Know your model's Toughness and Save, and your weapon's Strength, AP, and Damage, and you've got 98% of the game. Keep the codex on hand for the details. After a few games, return to the codex to start learning Stratagems, to take Enhancements, and all the other features your army offers.
No matter how deep into the rules you want to go, this codex is a great overview of the most iconic figures of the Warhammer 40,000 universe.