Up the Duff is great for week to week, "my uterus is the size of a grapefruit" type info! but I second New Active Birth, it is a must read IMO. It is easy to read and understand. The other book that I have really loved is Labour of Love by Gabrielle Targett. Fantastic. For heavier reading but still excellent information on childbirth, The Thinking Womans Guide to a Better Childbirth!