Your Pregnancy Bible, by Anne Deans is very good.......gives you info for every stage of pregnancy, in huge detail, but in a great easy to read format!
I have read it cover to cover a couple of times (Its a big book, and fully illustrated).
Also highly recommend The Rough Guide to Pregnancy and Birth - by Kaz Cooke - absolutely hilarious and a much more light hearted way of reading about pregnancy (covers all the serious aspects too, but a really fun read which will make you laugh, plus must be good as my hubby couldnt put it down).
Good Luck TTC.........and hope you get your BFP soon