Believe it or not, with each pregnancy the book(s) of choice changes. On the first one, the ultimate book is What to Expect When You're Expecting. Each chapter takes you through each month explaining the typical symptoms for that month, a description of how the baby is growing, and covering topics that may concern the mother. Easy to read and use as a reference. However, my sister-in-law hated the book because one of the explanations scared her unnecessarily when she was experiencing the symptoms.
Second time around, I referred to the aforementioned book only to find the symptoms of pregnancy since I had the book in stock. This time, I got two funny ones and one written by my doctor. The first is a parody of the What to Expect book called Expect the Unexpected When You're Expecting!: A Hilarious Look at the Trials and Tribulations of Pregnancy. It's every bit as hilarious as the title sounds. It's not meant to offer advice, but it does ring true on some of the facts.
We girls don't talk about everything when it comes to pregnancy. Instead, I turned to the The Girlfriends' Guide to Pregnancy: Or Everything Your Doctor Won't Tell You. The author makes you feel like you've gained a new best friend who tells you all her secrets, talks about those annoying women who bounce right back as soon as the baby pops out, and telling it like it is based on experience from a woman who had four kids.
For advice during the second pregnancy, I relied the most on my doctor's excellent 1000 Questions About Your Pregnancy: Everything Every Expecting Woman Needs to Know. The book is laid out in question and answer format sorted in groups like illness, medicine, early pregnancy, and so on. There is a fold out chart that gives you the highlights of the entire nine months. One thing I liked about Dr. Thurston is that he tells you like it is without the sugar-coating. Some may not like this, but it worked for me. Thanks to insurance, he isn't my current doctor.
Now that I am on #3? All the books are sitting on the bookshelf along with the other parenting books. I may have cracked open a book or two looking to verify pregnancy symptoms before it was time to take the test. If I have a question or can't remember something, then I'll pull them off the shelf and use them as a reference.