I bought this book after securing employment with a European Union institution, which would involve me living and working in a French speaking country. As a result, I needed resources to help make my French much cleaner and natural. I found it was a major part of my French improving, to the point where within 6-8 months, I could read EU Commission documents in French with 90%+ understanding. Strongly recommended, although you will need other types of book to augment your French. This book was a vital tool.
I was torn between buying this, and the extremely friendly looking "555" verbs by another publisher. My advice is do not believe that because this title only has 501 verbs, it is inferior. This book is superior to other titles for one main reason. That is, every verb is presented well, and various useful vocabulary items which have their root in that verb are shown as well. This allows you to build up your vocabulary as well as verb conjugation. There are also plenty of examples for each verb (c. 6-8 words), unlike other titles which may only have one or two.
The book is not without weaknesses. One weakness is it is not very portable, so if you want this book to carry around on holiday, forget it. Another slight weakness is that the explanation of verb tenses are not particularly "readable", full of technical linguistic terms that are unnecessary.
All in all, this book is an excellent resource for those wishing to learn French.