I grew up on fantasy and sci-fi and have spread from there. I've only read three books twice, mostly because there are so many new good authors to explore. McCaffrey's Dragon books were a nice read though I doubt I'd pick them up again. I enjoy many of the Discworld books for their dry humour. Recently I have enjoyed Brandon Sanderson's books and the wonderful First 15 Lives of Harry August by Clare North, and then read all the rest of hers. For a historical bent, The Chronicals of St mary's are an easy and fun read, and for female heroines in older times, Shelley Adina's Magnificent Devices series are nicely crafted. Hard Sci-Fi, no one beats Iain M. Banks, though Neil Stephenson also created wonderfully deep backstories to his cultures. I have 4,500 e-books and can only read a tenth of them, so I like to pick good things rather than bad.