I cannot say enough good things about The Birth Partner by Penny Simkin. In everything that I've read, both online and in print, this book is the most complete preparation for birth I have encountered. The first parts of the book describe the end of pregnancy and a detailed account of all parts of labor. The book then goes into coping methods for a natural birth, options for a medicated birth, and complications that can arise (and subsequent procedures). It ends with a little about post-birth, newborns and breastfeeding (although those are really topics for a whole different book).
The book very much focuses on how the birth partner (husband, family member, doula, etc) can help the mother during each stage of labor. Nevertheless, I found the detailed descriptions quite informative for myself. When contemplating my own birth plan, having all this knowledge made me focus on choices for various scenarios (i.e. what to put in the birth plan), but also the priorities of my directives (the must-haves vs. the would likes), and present those to my care provider.