Easy answer for me: John Wyndham. He, in my opinion, is the greatest science fiction author of all time. He hasn't produced many books, but they are all classics. The best is probably Day of the Triffids. The reason his books are so great is that they don't go in for big, exciting fight scenes and flowery language. Instead, he follows the daily life of people during an unnatural event. The heroes are not muscle bound hunks with no shirts and bazookas. They are ordinary (very 1950s british) men; journalists, bankers, managers, who in the face of a strange and unnerving situation can't do much but keep calm and carry on. Oh, and some of them are absolutely terrifying. Especially The Midwich Cuckoos. Especially if you put yourself in the shoes of one of the women.
