Here's another vote for Penny Simkin's The Birth Partner. I read The Birth Partner several years ago during my doula training and gave it to my husband to read a bit at a time throughout my pregnancy. It really helped him to imagine what our birth might realistically look/feel/sound like, gave him some concrete ways to be helpful during labor, and as a bonus spurred a lot of late night conversations between the two of us about our baby's development and coming birth. All in all, two thumbs way up!
I read a lot of books while I was training to be a doula and the one that I felt most compelled to revisit while I was pregnant was Ina May Gaskin's Spiritual Midwifery, for all of the wonderful, inspiring, empowering birth stories. Also, I wish that I had thought to revisit a breastfeeding book before my daughter was born! LLL's The Womanly Art of Breastfeeding and Kathelen Huggins' The Nursing Mother's Companion are my favorites. My first week or two establishing breastfeeding were challenging because my daughter was an extremely enthusiastic nurser but wasn't latched on in an ideal way and I was beyond sore...once I thought to pull out a book and review the section on controlling how your baby latches on, I was able to correct her latch. After a few days my nipples healed and we've been great since then. I just highly recommend adding a breastfeeding book to your "to read" list while still pregnant to try and avoid my mistake!