Forum Moderators: not2easy
Derivative works could include summaries, movie or TV screenplays, a line of T-shirts based on literary characters, all sorts of things.
As one example, the Reader's Digest pays generous royalties when they publish their summaries / adaptations of material originally published elsewhere.
If you're asking because you want to take part, and since you're an Affiliate Dreamer, you can apply a very simple test: is your summary/review for the purpose of getting affiliate profits by making Amazon sales, or is it to get profits by selling the summary?
If it's neither, and you want to get Adsense clicks, it had best be a real review, and not a summary.