Pregnancy for dummies is really good. Lots on great advice, especially when to worry, when not to worry and when to seek help. It's quite funny and not patronising either . Has good sections for men too.
If you have a partner who is involved, I fully suggest 'The Expectant Dad's Survival Guide' by Rob Kemp. I even read it myself and found it, in many ways, more helpful than all the clinical pregnancy books for women. But I would suggest any pregnant women get their partner to read it, as it's laddish enough for them to enjoy and relate to, but also extremely focused on how they can understand and make YOUR life easier during the pregnancy. His follow-up book for after the birth is less helpful though.
Your body, your birth your baby really helped me at the end of my pregnancy. More suited if your HR as is a lot about staying in control when you feel like your not in control. Pregnancy for Men was a funny read for my hband.
Bought quite a few pregnancy books....but hated them and gave them away, as got just about all the advice I needed on here during both pregnancies. And in a far more direct, less patronising way. Most of the stuff out there is v formulaic IME and written with a cutesy, twee tone which makes my teeth itch (What To Expect and Commando Dad, I'm looking at you).
That said, I'm told "Expecting Better" by Emily Oster is great, but it seems to be out of print at the moment.
"What Mothers Do" is brilliant, but more aimed at after the birth rather than pregnancy.