It is clear to most readers of The Silmarillion (and those who then go on to The Book of Unfinished Tales) that the strongest part of the story is the tale of tragic hero Túrin Turambar, cursed to achieve glorious deeds in battle and yet disastrous in his private life and his effect on those around him. But the Silmarillion account is too brief, and the Unfinished Tales version has large gaps in it.
Christopher Tolkien (now older than his father lived to be) has pulled together the various versions of his father's tale of families and war, and made something really special out of it. I have read both previous versions, and of course the Beowulf and Kalevala texts which inspired some of it, and I still couldn't put it down. Alan Lee's beautiful illustrations don't do any harm either. (Though I was slightly frustrated that the promised map of Beleriand doesn't appear.) (Edited to add: Oh yes it does; luned and pnh have found it for me.)
Those who have only read The Lord of the Rings and The Hobbit may be a bit confused by the setting, as Beleriand has of course sunk below the waves millennia before Bilbo Baggins left Bag End; unfortunately Christopher Tolkien's introduction to expain all this is rather tough going, more so than the main text itself. On the other hand, his appendix explaining how and why he compiled the story from his father's manuscripts as he did (for three different publications, differently each time) was surprisingly interesting.
There's lots to pull out from the text for those so inclined: it further illustrates what Tom Shippey has written about Tolkien and war and honour, but it's also the only major Tolkien work I can think of where family relationships play a crucial role in the plot. Strongly recommended.