Bob Shaw’s science fiction book “The Two-Timers” is engaging. Nine years before, Kate was discovered strangled and raped in a desolate park. In this standalone novel, Jack Breton defies time and enters a parallel universe to retrieve Kate. Though Kate is married to John, his double, in the opposite timeline. Either Jack or John has to pass away for one husband to stay. The novel weaves suspense and intrigue across its 192 pages.