Get to Grips with French Grammar is a real tour de force but at the same time easily accessible. It is comprehensive in its coverage and goes from the very basics of articles and noun genders to the more exotic emphatic pronouns, which I, myself, had not given much thought to.
The verb section is also excellent and presents each verb fully conjugated in several tenses. All of the example sentences are phrases that are genuinely useful in real life and not surreal, impractical statements that you can find in some books.
I think that like most people, I find formal grammar bit scary but this book certainly takes the fear out of it and explains a potentially difficult subject in a clear and effective way. It is certainly a great addition to my French grammar resources and I heartily recommend it.