I find the idea of the multiverse difficult to swallow. The what? The idea that there are billions of parallel universes like our own (only different!) seems a faith step to me (which is not a comment on whether it should be believed). But apparently the Everett interpretation of quantum theory says just that. (QT is one of physics’ fundamental theories—the other is relativity if I understand the lie of the land correctly.) This book review starts off at a sort of comprehensible level. Read the first paragraphs slowly to get a taste of the extraordinarily non-intuitive reality in which some scientists think we live and move and have our being. Amazing!