Words of Radiance is the second.
It's really good.
That's not much of a review, of course.
In the first book, we get a great deal of backstory on the character Kaladin, who is pretty much the first book's main character. This book's backstory is on another major character, Shallan.
Now, I'm not going to talk too much about it, but Kaladin's backstory is relatively predictable; we know a pretty fair bit about it from early on, and it follows paths I often saw coming. (This is no doubt colored by the fact that I've read TWoK at least three times, maybe four; I can't quite keep it straight in my head at this point.) Without ruining things overmuch, I can say: Shallan's backstory has a few twists in it that really took me by surprise.
This book also has some much bigger status quo shakeups than I was entirely expecting coming into it; I'd rather thought that there might be another book or two in between where things were at the end of TWoK and where they are at the end of WoR. Not that I mind.
What to say that isn't just nerdy nerdiness? Nothing I can think of. I can say that the ending of Words of Radiance left me super-excited for what's next, more so than the ending of The Way of Kings did.
I'm also a bit worried, because apparently Words of Radiance is literally as physically large as the current binding technology used by the publisher will allow, and the idea of the books' structure being limited that way genuinely upsets me. As I mentioned in the review for TWoK, these books would suffer if broken up into smaller ones than they want to be.
Anyway, we learn quite a bit more about the nature of the world this time around, which is great. (I realize, looking back, that I made no mention in the TWoK review of Shardblades and Shardplate. The Shardblades are particularly important in this specific book, and we learn some interesting things about them.) There's even more relatively cryptic references to others of the cosmere books that Sanderson has written, including a teaser for the best possible crossover teamup in all of the cosmere in the next book. I'd explain, but that would be too much of a spoiler for anyone who hasn't read the book.
(Of course, according to the author, the character in question has been part of the series since the early version of The Way of Kings that didn't really get published, and didn't appear in what the readers see as the "native" book for said character until years later from Sanderson's own perspective. Can you tell I'm really into this stuff?)
Anyway, good (long) read, five