Side-By-Side French and English Grammar is probably the best French Grammar book I have found.
It's not the most comprehensive (for deep research, I prefer the Berlitz French Grammar Handbook), but its the best for casual, quick hey, explain this concept to me in thirty seconds use. English grammar concept on the left page, corresponding French grammar concept on the right page.
Its the only French book I've borrowed from the library that I liked enough to buy for myself. For what that's worth.