Instruct: Classify Amazon reviews into positive or negative sentiment
Query: not really science fiction but speculative writing

Very good speculative book. It's about a genius that invent's a real truth-machine.Halperin just took what I just told you and speculated on and on , and wrote down EVERY possibility that branch out from having a reliable truth machine.The charecters have depth. the writing feels real , and the book as a whole is very realistic.In all , I would'nt categorize it as real sci-fi , but that aside , It's a good book.