For most things in met the best books are the ones written for glider pilots. One I found useful is 'Understanding Flying Weather' by Derk Piggott. It's not too big and intimidating either!
I suggest you try and get hold of the books to look through before you buy, as a style that suits one person may not suit another.
Also have a look on the 'net as there are some useful pictorial guides to cloud types with lots of photos. If you can't find them, let me know and I'll post links.