Cluster

I read bunches of Piers decades ago. This is one of his earlier works and one of the best from at least a dozen series of his I read. But it's still the best I've read out of literally thousands of sci-fi books for representing truly alien life forms. Truly excellent. And of course there are love affairs. But, the nice twist is that the human is inside an alien body every time. So it's the psychology which is making love, not the body. And well, there's some freaky sex also, but not lurid or salacious. Well done indeed. (From a comment, I made on a post looking for recommendations of inter-species love affairs.)

I remember details of few of the books I read back then, but I do remember this series, as it stood out. A novel and unique concept, well, back then, well executed, with an excellent play on the discrepancies between various psychologies, with the hero being a somewhat primitive fellow, but, not, as many automatically assume, stupid and unsophisticated. The hero is neither, after his own fashion. I've been fortunate to extensively interact with a real-life version, but that's another story.

This series provides everything good storytelling has to offer, with the bonus of also being excellent sci-fi. The tour of a potential universe with all its diversity is well worth the read alone. One of the all-time top series I've read.