Overall, helpful. If you’ve done work on this before, you won’t find much new in the first few chapters, though I think these make the book great for discipleship (or evangelism) in teaching someone the error of the prosperity gospel, biblically speaking. They put everything together for us in sequence.
The last couple of chapters were some of the most helpful, addressing the salvation of those captured by this teaching (salvation’s possible but very low confidence), if we should associate with prosperity teachers in any way (with leaders and purporters, no; with sheep gone astray, yes) and how the prosperity gospel might make its way into our lives without us knowing it (e.g., see David Platt’s Radical for a full length treatment).