de Camp (World 65)
L. Sprague de Camp (1907 – 2000; first SF publication, 1937) was a prolific writer of both science fiction and fantasy. (My favorite fantasies are his Harold Shea stories written with Fletcher Pratt, beginning with The Incomplete Enchanter.) His SF stories include Lest Darkness Fall, The Wheels of If and A Gun for Dinosaur — dealing with time travel and alternative history — and my favorites, the Viagens Interplanetarias stories of tours to Krishna (orbiting Tau Ceti) and other worlds.
Krishna is a relatively primitive world, and much of the machinations in the stories deal with the interplanetary travellers’ attempts to keep all modern technology (including the fact that interplanetary travel is possible) from influencing the world — basically Star Trek’s Prime Directive, fifteen years earlier. Since all Krishna natives are green-skinned and have antennae, maintaining the disguising makeup and prosthetics alone is a challenge. The Krishna novels all have a “Z” in the title: The Queen of Zamba, The Hand of Zei, The Hostage of Zir, and so forth. Rather than a common protagonist, they share a common setting, with the machinations of various travellers on interplanetary tours keying the plots.