Birth and Beyond by Dr Yehudi Gordon
If there is only one book that you would read (highly unlikely) when preparing for birth, and you'd want to know what to expect when expecting - then the "Birth and Beyond - the Definitive Guide to your Pregnancy, Your Birth, Your Family - From Minus 9 to to Plus 9 Months" book by Dr Yehudi Gordon is what I would highly recommend.
There is nothing that he does not cover and it's written beautifully - when I look back at my own birth stories I could not have followed that book more if I tried.