Three books that I'm a big fan of are:
What's going on in there - How the brain and mind develop in the first five years of life by Lise Eliot (my aka: the brain book):
It has become the basis of my knowledge on baby development and what I judge all other book discussions by. A strong scientific piece of writing that is easily understood by the non-bio me.
Only downside is the binding's not that great on the English version (hubby has the Chinese version and it's fine there). Not a big problem here in Taiwan because it's quick, easy and cheap to get books re-bound.
Your self-confident baby - How to encourage your child's natural abilities from the very start by Magda Gerber:
This is a baby/toddler development/attached philosophy that speaks to me (called the RIE philosophy). I feel RIE gives a good balance to life, makes intrinsic sense to me, and is facinating. The focus is on allowing a baby to explore and develop at his or own pace and to his or her own interests.
The diaper-free baby - The natural toilet training alternative by Christine Gross-loh:
A good book on elimination communication (some other books on EC are not so good); it is balanced, not overbearing, not fanatic and not pushy. I think it goes along the lines of RIE (respecting and communicating with baby...rather than having the goal of having a potty trained infant). I thought it was great as it gave me an understanding for how we can make it work within our life-style to the degree we are comfortable with.