I particularly like this one because as with most Tina Bruce books, it is quite easy to follow and she tends to explain things in plain language, which is always helpful! I've got a load of different books but it would depend on what you were looking at.
If you're after theory, then Hali recommended a brilliant book when I started my FD. It's by Linda Pound entitled "How children learn". It was quite a cheap book and explains theory in really simple language. I found this book useful as a basis for researching the different theories in more detail.
Erm... if there is a particular book you are thinking of, let me know and I'll see if I've got it