ACE DOUBLE: THE COILS OF TIME + INTO THE ALTERNATE UNIVERSE

Ace Double paperback, 1964. Cover by Jack Gaughan.

"Dr. Henshaw had created what he thought was a time travel machine and he had sent guinea pigs through it. But now he needed a human guinea pig to test it with. 

Christopher Wilkinson thought the whole idea was absurd, until a book that had been sent through the machine came back with a thumb print on it, the finger print of Vanessa, his long lost sweetheart! 

So Wilkinson agreed to the experiment. He stood in the white circle facing the machine as it began to gleam and spin, pulling him down through the tortuous coils of time...."

Ace Double paperback, 1964. Cover by Ed Valigursky.

"Others called their expedition a "wild ghost chase." But for Space Commodore John Grimes and the beautiful Sonya Verrill who had initiated the project, it was strictly scientific research. Their trip along the rim of the galaxy in search of two men - two dead men - was also an investigation of the long-puzzling phenomenon of the Rim Ghosts. They would do this by penetrating into alternate universes. 

There was only one real problem involved in this study - how to report its results. For once the break-through to an alternate world was achieved, there was no known way of getting out...."