Not quite as compelling as the first, but man, still a mind-bender. Mild spoiler here is it does travel into the past. One of the things that makes "Wool" so good is it is entirely in the future. That provides the prose some latitude and that can help make or break a book when it starts to get into the awkward drama around social mechanics and institutions we are already familiar with. Anyway, before you read this write down the Silo numbers from wool, and the names of the key characters. Also don't look up anything online because spoilers abound.