[thelawnet]

There are three basic general guides:

Mushrooms - Roger Phillips
The Encyclopedia of Fungi of Britain and Europe - Michael Jordan
Collins Complete British Mushrooms and Toadstools - Barry Hughes

You would perhaps do well to buy all three, each has its place. The Collins book is smallest and actually covers most species (which is very handy), but it generally doesn't have gill shots as the larger books do, so it is typically harder to do picture identification using this one. It also does not cover edibles, generally speaking.

The Phillips book IMO has the clearest pictures as they show the fungus and its characteristics 'in the lab', rather than the in situ photos used in the other books - pretty, but not especially useful (the text will say something like 'mixed woodlands' in any case).

The Jordan book is pretty similar, though slightly smaller, it is still not terribly portable for field use - something the Collins excels at, though I personally struggle with the small pictures in Collins and find it quicker just to carry a larger book. The Jordan book is the only one with a key, very helpful if you've no idea what genus your specimen is in.

Best to buy all three.....