I read the first book, interesting but too fantastic. Mercifully we don’t get TV so I haven’t had to witness the ultimate “it fails in comparison to the book” syndrome.
Actually, it doesn't. I saw season 1 before reading the book. The season had a little bit of closure, but I figured it was left open for season 2. Not really. The book has no particular ending. (In fact, part of the beginning of book 2 was taking out of book 1.)
The thing about the first series is that there are these independent story lines which never merge or overlap. There's a promise that they will in the future, but we don't get to see it. Hell, there isn't even much of a hint of it with the mortality rate as it is.