The best cosmology book I've ever read. Forget about tedious Elegant Universe, forget about that slapdash Brief History of Time, this is the book to read to get a an overview of our current understanding of the universe as a whole.
Obviously the main argument presented in this book, of cosmological natural selection, is nothing more than a hypothesis of truly fascinating potential and implication. But in presented the whole of his argument Smolin takes the reader on a whirlwind tour of space and time, how we know what we know about them, how we've gone about asking the questions and what that reveals about us, and the currently competing answers for the wildest questions humanity has ever dared itself to ask.