Ten years ago I was headed to France on business, and picked up a teach-yourself-French book ('Idiot's Guide'). I learned some phrases, some pronunciation, some grammar, and some vocabulary. Then last year when I got serious about learning the language, I found Laura Lawless and her 'Intermediate French for Dummies'. What a revelation. It was over my head, as a beginning speaker, but I liked the logical layout of the book, and I felt I was really making progress. This is a grammar self-study guide par excellence. No culture tips, no map of France, no cartoons of Parisian bistros. And no pronunciation guides. But you will find clear explanations of the parts of speech (which are different in French than English, a fact which surprised me), the difference between reflexive and pronomial verbs, and the devious usages of pronouns and prepositions. And a guide to using bilingual dictionaries.
The chapters are self-contained, in that they can be studied in any order, and do not depend on each other to any great extent. There are self-tests at the end of every chapter, and while not exhaustive, they illustrate the subject of the lesson, and are a good reinforcement of the material.
The author has a very easy writing style, breezy but not chatty, authoritative but not dry. She's been a guide at About.com since 1999, for their French Language section, and on that site she has assembled an impressive self-study curriculum and community of Francophones. She has expanded the lessons in this book to a very detailed level, and has a number of native speakers who host on the forums and help answer the knottiest questions. There are forums for beginners, intermediates, and advanced speakers, as well as a section for teachers of French. The extensive quizzes are especially good. I believe that the experience on the website helped shape this book, with clear examples and an adult to adult tone.
Notwithstanding the excellent web presence, I still refer to this book because it is so handy (meaning I can handle it and write notes to myself in it) and because it is so easy to navigate. I have gone through it once, filling in the exercises in pencil, and I'm about to go back with an eraser to clean them up, and then fill them in again. Repetition and repetition is how I learn, but first someone has to explain it clearly, like Laura does in this book.