303 Tricky Chess Tactics

I found the following tactics puzzles exercise book very useful:

http://www.amazon.co.uk/303-Tricky-Chess-Tactics-Training/dp/1580420761/ref=sr_1_1?ie=UTF8&s=books&qid=1270649230&sr=8-1

I think it is aimed primarily at intermediate players ...

It could possibly be used as part of Michael De La Maza'a 7 circles training etc.