I've been a rereader ever since reading was a serious source of enjoyment. I'd reread my Marvel comics, for one thing. Once I'd discovered Tolkien's Middle-earth books and Lewis's Narnian books, etc., I was a rereader of books. Lewis says somewhere that, with good books, you generally can't really enjoy the book deeply till you reread it, because the first time you may just so focused on the pleasure of finding out what happens next. But in something worth rereading, that's only one element of the pleasure. Among the eminently rereadable authors of science fiction and fantasy I count Arthur Machen, H. P. Lovecraft, H. G. Wells, Fritz Leiber (for "A Pail of Air" and a few other stories, but not for the Fafhrd stuff), G. K. Chesterton (The Man Who Was Thursday), George MacDonald (Lilith, etc.), Wilson Tucker (The Year of the Quiet Sun), Algis Budrys (Who?, Rogue Moon), C. L. Moore (for "Vintage Season" etc.)....