This review starts with the (this time very few) bad things then gets to the more positive things. Please keep that in mind.
First of all, having all those indexes is neat - except for the rather awkward fact that they are using page numbers instead of the plot numbers. Each plot is numbered in the book, with the number printed in big letters in the same line as the individual plot's title, really easy to see. Thus, I don't see a reason why the plot numbers are not used for indexing. Instead, we get page numbers in plain face and in bold, depending on whether one or two plots on that page fit the index criteria. Definitely not elegant, especially since the plot numbers would immediately identify the genre under which an item is initially presented (1-167 = Fantasy, 168 - 334 = SF, 335 - 501 = Horror)
Secondly, it is a bit disappointing that the individual plots are not clearly marked as being one or more sub genres as presented. Instead, you only know the main genre (fantasy, SF, horror) and to which sub genres it can be adapted easily. It would have been nice if next to the title of the plot, there was also in lighter colour the sub genre the author had in mind when writing the plot.
Third, on a personal note, I find the definition of anime actually used in tagging plots rather ideosyncratic. That is, I would have expected it to be strongly linked to emotions and emotional issues, but I have the impression that the easily adaptable to column more joins it with action stunts.
Fourth, it is noteworthy that there are no real repetitions, not even cross-genre. Each of the 501 plots is unique, maybe sometimes similar in the initial situation to an earlier plot, but in its meat a beast of its own.
Fifth, this is definitely noteworthy given just how much material is in there. Think about it, 501 plots, each of which is a small tale with one or more surprises or twists. There is a lot of inspiration to be found.
Sixth, combined, this also results in there being probably something for every taste, although I sometimes had the impression that certain genres and certain styles combined rather often (like a seemingly high adaptability of horror plots to action horror). If you are looking for inspiration, you are likely to find it. Especially if you consider the broader usage of the plots - many include ideosyncratic NPCs which you can add to your own campaigns adventures without necessarily adopting the entire plot. There is really a lot of material you can mine to support whatever you are up to.
Personally, I think this is a very good product, which is why I gave it the top rating despite the minor negative points I mentioned above. If you want some inspiration or just a nice read of various plots, I heartily recommend this book.