French in Action
Workbook - First Edition - Part I
Overview
If you want a brand new French in Action workbook, the third edition will be the easiest to find at large retailers. I would not hesitate to use any edition. When buying the French in Action workbooks the most important thing is to buy clean copies without the answers of someone else in the blanks. My favorite edition of the French in Action workbook is the second edition. The second edition has more material than the first edition and it avoids the affectations of the third edition (e.g. Marie-Laure's Twitter feed.) What is more, the second edition (as of this writing) is the most readily available (often relatively inexpensively) in used bookstores.
Second Edition Versus the First
From the book itself:
In the workbooks, learning activities have been reorganized for greater effectiveness and ease of use. The authors have added a variety of new writing and reading exercises designed to expand students' ability to communicate through writing and to understand by reading contextually.
Buying
Shop around; the price can sometimes vary among retailers. You also may have good success searching at second-hand stores and on eBay.