Like much of the existing Tolkien work outside of The Hobbit and Lord of the Rings (LOTR), the content of Children of Húrin was written long ago and stashed in Tolkien's writing desk for half a century. Parts of the story were published here and there, including in the The Silmarillion, but it wasn't until 2007 that those fragments got assembled into a single, continuous narrative. I recently read Children of Húrin and this is my review of it.
My short review is this: The story is very good. But the storytelling is pretty obtuse. If you're a Tolkien fan, you'll probably enjoy this story for what it reveals about Middle Earth, but you aren't likely to fall in love with any of the characters because you won't feel like you know any of them. Like The Silmarillion, this is Tolkien at his stodgiest. He's relating history instead of a "faery story" like The Hobbit.
From this point, there are some spoilers in my review, so don't read on if you intend to read the book yourself.
Back in the 1980s, there was a Incredible Hulk TV show starring Bill Bixby, and it featured an intro designed to get new viewers familiar with the premise in roughly 30 seconds:
Doctor David Banner. Doctor, physician, scientist, searching for a way to tap into the hidden strengths that all humans have. Then an accidental overdose of gamma radiation alters his body chemistry. And now when David Banner grows angry out outraged, a startling metamorphosis occurs. [Cue footage of Lou Ferrigno as Incredible Hulk]
That's basically Children of Húrin. Set in the First Age of Middle Earth, the children of Húrin are cursed upon birth. Húrin goes missing, and his daughter Urwen dies at a young age. Húrin's wife Morwen sends their son Túrin away to go live in Doriath. This begins his life as a wanderer, and a whole series of adventures and quests that includes fighting orcs, joining a band of outlaws, consorting with rogue dwarves, and facing the terrible dragon Glaurung.
The thing is, Túrin has a temper. He's a hot-head, and frankly he's got the skills to back it up. The guy's a hero because he's good at what he does, and what he does is swing a black sword around until it kills a bunch of your enemies. He's exactly the kind of hero I'd have adored as a kid. If you prefer Strider over Aragorn (so to speak) in LOTR, then you're going to love Túrin. He's everything you imagined Strider to be before we met him in LOTR.
The problem with Children of Túrin, for me, is that it's under-written. As with The Silmarillion, the prose is overly grandiose and stilted, using archaic language, and favouring events as they happened over the [fictional] people who made the events happen. There are lots of names in the book, and of them all you mostly know Túrin and maybe Mim (the dwarf from The Silmarillion). I felt like I knew Mim about as well as I knew Túrin, even though there are only a few chapters of Mim compared to a whole book of Túrin.
I imagine I'll forever be confounded by Tolkien's steady decline from delightfully personal narrator to puffed-up scholarly commentanor. To be fair, Tolkien has rightful claim to use the archaic language he gravitated toward in the end, but I think most readers even 70 years ago would have found his prose dispassionate. I've read stories from the past. Jules Verne and Edgar Rice Burroughs and Marie Corelli and Robert E Howard and even Lovecraft pre-date Tolkien as authors, and their storytelling is vibrant and personable and effective. Tolkien's posthumous volumes are drab by comparison, and it's frustrating to me because the story of Túrin is among Tolkien's best work.
I have to remind myself that posthumous publications of Tolkien's writings are likely not what he'd have published, himself. It's hard to believe, but he wasn't actually a professional author. He wrote this stuff in his spare time, unbelievably. He didn't finish Children of Túrin or The Silmarillion or all the other myriad stories in the entire history of Middle Earth. I like to imagine that if he'd somehow thought to make writing his day job, he'd have had the chance to finish those stories with the same heart and passion he put into The Hobbit and Fellowship.
I cannot fathom why the one LOTR TV show we'll probably ever get was not Children of Túrin. Túrin is Tolkien's Conan, and his adventures are just as entertaining and often more fantastic (meaning, literally, that they contain more "fantasy" elements). The story is fantastic, the characters feel like they'd be fun to get to know better, and the setting is an earlier version of the Middle Earth that most of us know.
If you're a Tolkien fan, you should read this book. If you're a Tolkien fan who finds Books II to IV of LOTR difficult to get through, then just read the summary on [The One Ring Wiki](Two Towers and Return of the King). It does a good job of hitting all the major points of the story, and it does it efficiently, in plain English, with about as much passion as the book's author did.