This book provides an introduction to quantum gravity aimed at the general public. It provides three different approaches to quantum gravity, doing a decent job of discussing the strengths and weaknesses of each. The author discusses black holes and multiple universes in the journey.
His approach to each subject is historical, tracing development of key idea and briefly mentioning the people involved.
Overall the book is interesting and a rather light read. Although it is aimed at the general public, it is probably a little light for the people who would be interested in reading it.