Textbook
My Pick for the Most Charming Part of the Program
The French in Action textbook complements the program's video learning with both supporting material and incremental information. The amusing illustrations and other content are very entertaining, and endearing in their own right.
Choosing a Textbook (Which Edition?)
Skip the first edition, which is light on content. Strive to acquire the second edition. It is the most charming and has all the great content without the more modern affectations. Also, the second edition encompasses both Part I and II, so you only have to buy one book.
Buy the third edition if you prefer a brand-new copy and/or want the convenience of one-click shopping (the second edition may be more difficult to find). The affectations are slight, so they really do not get in the way of the core material. One example is the inclusion of Marie-Laure's "Twitter" feed (so, since Twitter became X, even this update is now out of date).
If you do choose the third edition, know that you will not need to buy Part II until you approach the end of Part I.