The Door Into Summer

From the first page of the Signet 6th printing: "An electronics engineer invents a wizard robot... only to find himself shanghaied by his ruthless partner and his gold-digging fiancee. The crafty pair forces him to submit to the "long sleep" - suspended animation for thirty years. But when he wakes up in the year 2000 A.D. the inventor makes a startling discovery. He learns that it is possible now to twist time forwards or backwards. And so he returns to the past bent on a mission... of revenge."