I won’t give it up, but my feelings are quite mixed. On one hand, I totally didn’t see it coming, and he did, technically, give the reader all of the information necessary to figure things out.
On the other hand, I feel less oustsmarted (which is good) than tricked (which is bad), and I may have to take away the compliments I paid to Horowitz about his handling of the Holmes canon. While very clever, I think his ending made Holmes seem dimmer than is fair.
I have some other issues, but it’s hard for me to criticize them without giving up the ending, and I really don’t want to do that. This is a book, whatever its faults, very, very much worth reading. I still recommend it wholeheartedly.
Final rating: I’m not good at star ratings. Thumbs up with reservations. If you like Sherlock Holmes, check it out.