Parallel Worlds: A Journey Through Creation, Higher Dimensions, and the Future of the Cosmos by Department of Physics Michio Kaku (Paperback / softback)
Understand the universe we live in? No? Neither do the experts either but they can explain why they don't.
Superbly written, with excellent use of analogies for non-physicists. Clarifies difficult subject matter extremely coherently. Don't expect to sit and read this through like a detective novel. It's dense and and difficult material but it's a brilliant book for anyone interested remotely in the cosmos and universe we live in. It raises as many questions as it answers. I've found myself sitting and reading maybe 6-10 pages then pausing a while to ponder the concepts that I've just read about. Very highly recommended.