here, but by way of a brief recap, in the near future humans live in a large underground 'silo' (think of a cylindrical 150 storey tower block buried in the ground). How they got there is a mystery but the very air outside is poisonous and as far as they are aware they are the only people left of mankind. They don't know much about 'before' only occasional picture books, strange stories handed down through the generations and the like.
In a desperate attempt to avoid any spoilers for Wool, I'll just say that Shift is a prequel that 'catches up' by the end of the book with the events in Wool. Shift is divided into three parts, or 'Shifts'.The first part of the book is a real futuristic rip-roaring thriller set initially in the mid 21st century, in a world not unlike ours today. You learn some of how the world of Wool and the Silo comes about. The end of the world scenario here is one of the scariest I've ever come about, and is definitely plausible. I've heard people say that you don't need to have read Wool to read this, and while as far as it goes this is true, you are going to get so much more out of it for having read Wool first. So please, please don't go straight into Shift. The second and third parts move forward in time and start to catch up with 'Wool'. By the end of Shift you are at exactly the same time as you are at the end of Wool (in fact I think the same conversation happens in each but I'd have to go back and check). Now normally, I don't like this kind of setup, i.e. knowing what's going to happen, but Shift isn't like that at all. They are two very, very different stories, and knowing roughly when the book ends doesn't mean you have any idea 'how' it ends or what happens to all the characters in Shift. The main characters in Wool don't appear until the final pages of Shift. One of the minor characters in Wool - Solo - has a big role in part 3 of Shift, but this is really good and fills in this characters story which I was really wanting to learn more about when I was reading Wool.
What I'm trying to say - badly - is that Shift just really works, so, so well, despite the fact that the whole prequel/catch-up mechanism shouldn't really work, not in my mind anyway. The first half of the book is in my mind (and in the opinion of some other reviewers) better than the second half, but that doesn't detract from the book at all. The first half of this book is the best fiction writing I've read this year and I've read at least 30 books so far. In fact overall I think the only book that's rivalling this year is its predecessor. Just like Wool, I'm giving this 5 stars on Goodreads. Can't wait to read Dust, which comes out in hardback next week in the UK (already out in paperback in the US), but actually is already out in the Kindle store - whoop!