The Wraparound Universe
The book starts with a look at the difference between a finite and an infinite universe, and shows how general relativity explains gravity in terms of curvature of spacetime. The reader is then introduced to topology, and Luminet describes how the universe might wrap around on itself in a topological sense, even though this doesn't show up in geometrical measurements. He goes on to look at ways that such wraparound might be detected - seeing the same galaxy in different parts of the sky would be an obvious way, but it would also leave it's mark on the patterns of the cosmological microwave background.
The later parts of the book take a wider look at cosmology, describing some of the history of the subject - Luminet feels that the contribution of Lemaitre should be more widely recognised. The book has short chapters and plenty of illustrations, making it easy to read. It is also clearly meant to be the sort of book you dip into at random. Some people might find it a bit unstructured for their purposes, but I found it a highly enjoyable read, giving an alternative view of cosmology which may just turn out to be the right one.