I picked up this title because I generally like Frederik Pohl's SF. I got a few pages in, thought, "Hmmm, this sounds familiar." A few pages more, and I realized this was a classic that I'd read when it first came out in 1977! Well worth the read!
From back cover:
Deep in space is a universe gone mad.
Ross took on the field assignment for a lark. But the routine business trip catapulted him into a brain-blasting mission to a galzxy of alien world: A utopia ruled by ancients where youth was the greatest sin, a society dominated by savage Amazons where being male was the lowest crime, a coin-operated wasteland where the prime law was conformity.
Tomorrow's terrifying marketplace where one man bargained for humanity's fate.