This Tor review says:

The technological innovation is “slow glass” a form of glass that by complicated scientific gobbledegook handwavium slows down light passing through it, so that what you see through a window made of it is yesterday, or ten years ago, depending on how the glass was tuned.

This is not a comedy, but Bob Shaw could never resist slipping in a joke here and there—and some of the jokes here read like out-takes from his Serious Scientific Talks. Garrod and his chief engineer trade jokes about famous scientists in school “Make up your mind, Heisenberg!” “Stop fiddling with that belt, Van Allen!” I can almost hear him saying the lines—in person he was one of the most consistently and spontaneously funny people I’ve ever met.

It sounds pretty good, actually. It's a difficult thing for the cover to convey well.

And hence it doesn't. Nice rendering of a 1974 California convention center, though.