The observatory presented itself to their eyes as a self-contained little community, without neighbours, and perched on the extreme end of the land. There were three buildings: a small, stone—built dwelling house, a low workshop, and, about two hundred yards farther north, a square tower of granite masonry, seventy feet in height.This SF novel from 1920 is about a chap called Maskull who is rather mystically translated from a Scottish observatory to the planet Tormance, orbiting the double star that we know as Arcturus, where he meets various inhabitants for deep and meaningful conversations, and ends up killing most of them at the end of their respective chapters. It clearly inspired C.S. Lewis, who took a lot of concepts from this for Out Of The Silent Planet and Perelandra, except that frankly Lewis did it better, by having vaguely interesting characters and by using comprehensible philosophical dilemmas - both being areas that A Voyage To Arcturus falls down on.
Tolkien also loved the book; Wikipedia quotes Colin Wilson and Clive Barker as singing its praises. I find it difficult to enjoy because I have read a lot of the better, later stuff that it inspired. In that sense, perhaps it's a hidden taproot text for the mid-century British SF writers, unconstrained by any need to be loyal to the (hazy) scientific facts, free to think romantically and even morally about other worlds. Neil Gaiman and Kim Newman quote a critic of an early splatter film as saying "It's like a Walt Whitman poem—it’s no good, but it’s the first of its type and therefore deserves a certain position." I felt a bit like that about A Voyage To Arcturus.
This was the most popular book on my unread pile acquired last year. Next on that list is Angels and Visitations, by Neil Gaiman.