Occam's Razor, a 1957 novel by David Duncan, can be borrowed (for free but registration required) from the Internet Archive. You may have read the 1962 Four Square Books edition.
From a review by P. Schuyler Miller in Astounding Science Fiction, May 1958, available at the Internet Archive:
I'll grant that there is nothing very original about the theme Duncan has used, of a man and woman, slightly strange, coming out of a parallel world and causing consternation and carnage in ours. The nominal science—the gimmick—that he uses is, however, more plausible than those in his earlier novels. He proposes a theory of discontinuous—he might have said quantized—time, such that the events of our universe occur in a series of pulses, while an infinite number of other universes co-exist with ours in the intervals while our time has paused and theirs is flowing.
Lael and Bel-Abon, primitives from one of these other worlds, are snatched into ours when something never quite explained occurs in an island laboratory. The author uses another new gimmick here, tremendously visual in its possibilities if he hopes to sell his book to Hollywood: the weirdly curved surfaces formed by soap films stretched from complexly warped wires. Since a war is pending, security is at a peak, and the immediate result of this innocent invasion is bloodshed and destmction, in which the laboratory is wrecked and assorted people killed. Eventually reason prevails, data are pooled, and Lael is sent home.
From a very long and detailed review by Damon Knight in Science Fiction Stories, May 1958 which is, also available at the Internet Archive:
At a naval base on Santa Felicia Island, Dr. Roger Staghorn keeps a complicated apparatus for the study of soap films. The base is the one where the first Moon rocicet, Luna One, is being prepared for launching. Staghorn is on the premises
because his specialty, the theory of minimals, has a bearing on the"plotting of orbits.
The excuse is pretty thin, but so are Staghorn and his soap films; both are fascinating. I spent a happy and incredulous half hour making wire frameworks according to the book's directions, and dipping them in soapy water. (How many planes of soap film will there be on a cubical wire frame? Six? Wrong — thirteen. Try it and see.)
Staghorn is a completely engaging character, a cadaverous scarecrow of a man with a compulsive rudeness toward authority. During a demonstration, he so provokes a torpid young ensign that when three films appear where only two are possible, the ensign breaks the extra one: and the anomaly refuses to repeat itself. Greatly upset, Staghorn goes back to his lab to tinker with the big soap-film machine, and from there the base psychiatrist, Cameron Hume, gets a phone call for help.
He finds the lab in darkness; two half-seen forms escape. Staghorn is lying in the
apparatus, knocked out. When he comes to, it develops that he has amnesia, and can't tell anybody what happened.
Now we get a series of incidents in which other people see the two who mysteriously appeared in the lab; through these repetitive glimpses we learn that the man looks like the Devil and the woman like Eve. They are wandering around the base, obviously bewildered; the man has great strength and kills several people who
try to stop him.
