I love the books of Vonnegut, Hamsun, Faulkner, and Nabokov; I really enjoy books on mythology (except those written by various "wizards" and neopagans), as well as medieval books; among contemporary writers, I especially appreciate Pratchett and H. van Zeijck:)
But my absolute favorite author is Tolkien. What I like so much about him, I don't know, but for some reason, he simply stands out from the rest...
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