I'm a book addict too! Even with all the internet at my disposal, there's still something special about having a book you can dip into as and when you feel like it.
I've tried to buy books that focus on different things or present themselves differently so I'm not reading the same thing over and over. I've got the "day-by-day pregnancy book", which has a page and photo for every single day and I only allow myself to read up to where I'm at. I've got the "what to expect" book which is more in-depth and text based. I also have the "rough guide", which is a more casual author-centric book, and finally the "best friend's guide" which is another personal account though I'm less keen on this one.
Oh, I also have the table book "a child is born" with all it's pretty pictures. I intend to buy Ina May's childbirth one as well.
I particularly love books with cutting edge pictures and scans.
