A book that was recommended to me by Casual Hero
is "Food for Free" by Richard Mabey, published by Collins.

It has diagrams, photos and recipes!

They have a pocket Guide and a 'normal' size. I have the pocket size, and its very good. It orientated towards food obviously <img src="images/graemlins/wink.gif" alt="" /> as opposed to general uses.

Have you looked at the Riverside Cottage guy's books (Richard something?)? I haven't but heard they're good for plants for food.