Encore Tricolore 4: Nouvelle Edition
I managed to attain an A* in GCSE with the help of my French teacher and this book - not only does it provide good exercises (that usually get set in class or as homework), but it also has a comprehensive list of vocabulary, and even better, a massive grammar and verb section. Particularly useful for those of us that struggle with that aspect of French, as it explains all of those complicated little details that we need to know, and in an easy-to-understand layout. 5* Amazon review