Sideslip (1968) by Ted White & Dave Van Arnam

One minute I was in New York . . . walking down Sixth Avenue, a private eye on a two-bit job . . .
Next minute I was in New York . . . a crazy town I almost recognised - but Goebbels was speaking in Union square, Hitler invited me to a cocktail party, and aliens from outer space were running the whole show. Fun City it wasn't . . .

Plucked from his own "time", a pawn in a Galactic power play, Ron Archer fights his way through a deadly maze of intrigue and conspiracy to an incredible destiny at the end of the star lanes!

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