While you can find many of the suggestions here in other books on self-editing, you'll also find advice that moves in new directions. There's a section on how to apply other people's suggestions to your own work that talks about the ways in which you can dig through surface-level criticism to get to the really helpful information underneath it. Many of Heffron's prompts in the section "Mining for Diamonds" focus on various ways to look at a piece of writing, pick out what's working and what isn't, and go from there.
Do you want help generating ideas? Evaluating your ideas? Making them serve the greater needs of your specific writing projects? What about using them to help you overcome various problems you'll encounter while writing--such as difficult beginnings, stuck middles, and troubled endings? The book follows up its instruction with helpful questions you can ask yourself, and expands on those with prompts and exercises to help you apply what you've learned to a specific piece of writing.
This book has a lot more practical information in it than the "idea book", and it's more versatile. It isn't meant for the seasoned pro, but novice and intermediate writers can learn a lot from it. My only minor gripe is that, in the beginning of the book, Heffron has developed a world-weary tone that focuses not on the wonder of writing, but rather on the mistakes that apprentice writers tend to make over and over again. In some ways this is good--he spends plenty of space on concrete suggestions and prompts meant to help you spot and conquer these issues. On the other hand, it's less inspiring and uplifting than the tone he takes in his previous book.
This is a wonderful book that could help most writers to improve their writing. Heffron is such a fixture in the editing world that you'll find his name somewhere in most of the writers' books out there--he really knows what he's doing, and he's sharing that valuable information with us.