I also like Dr. Sears’ The Baby Book. That’s been my go-to book for those “is this normal?” moments.
The Happiest Baby on the Block is also GREAT for newborns. There’s a video, too, which I found more helpful than the book, but either is invaluable.
You might want to have a variety of sleep books – there are a lot of schools of thought out there, so I don’t know if you want to promote one over another.
For labor, I can’t think of a better book than The Big Book of Birth. It has so much helpful information, and it’s presented in a very “you can do this!” way that I found empowering. I’ve loaned my copy out, let’s see… 5 times in the 13 months since my son was born!
If you’re dealing with working moms, I like The Milk Memos. It isn’t a how-to, it’s more of a journal by a few working/pumping moms. I got some good ideas and “support” from reading it.
It’s hard to find now, but The Wonder Weeks can be helpful in dealing with fussy stages. It talks about what the baby is going through developmentally, so even though they’re fussy, it can be easier to have sympathy for them (and help you figure out what they need/want).
For toddlers and up, I like Unplugged Play. My folks gave it to me last month for my son’s first birthday, and it has some fun ideas in it. Also helpful is the Ames & Ilg series, Your One-Year-Old, Your Two-Year-Old, etc. I think they go up to 6 or 7 years old.
And a great one for expectant parents (whether it’s the first baby or not) is And Baby Makes Three. It’s about maintaining a healthy and loving relationship even with the stresses of new-parenthood. Full disclosure: I work for the institute founded by the authors so I know them – but it’s a really great book.
On preview: Oh yeah, I second WhyNot’s suggestion of Touchpoints - how could I forget? It’s really helpful and low-anxiety. Very good.