Instruct: Classify an Amazon review into positive or negative sentiment.
Query: Delightfully mind-bending!

This is a wonderful book: a time-travel-mystery in which the fate of the universe and the outcome of World War II hinge upon the right folks falling in love 60 years earlier, assisted (or perhaps impeded) by meddling historians from 2057. OK, it sounds silly but it's an awful lot of fun. Highly recommeded for anyone who enjoyed Bull & Brust's "Freedom and Necessity", or (for very different reasons) Poul Anderson's stories of the Time Patrol. Four stars because it doesn't reach the pinnacles of perfection (there *are* a few books I'd rate higher), but I'd give it 4 and a half if I could.