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.
Richard Adams. Not only did he write Watership Down, my favorite book, but he always had such a unique style of writing as well as storytelling. He used vague language, not in a precocious effort to appear intelligent, but to write a different story for each reader. The endings to books like Shardik and Tales are great as well.
Frank Beddor, mainly because he wrote "the looking glass wars" which is my favorite book, and he balances every character out, unlike "Harry Potter" where the attention is mostly drawn around Harry.
My famous authors have got to be: zac power by h.i. larry and no i'm not still reading these i choose him because he used to make these books about adventure thrills and fighting. next i chose Wayne Thomas Batson he simply gets it for having a real/fantasy books in which they have humans,skrillax (giant spiders),stone blood and other mythical characters.
Rick Riordan is an awesome author, he wrote the Percy Jackson series which the last book comes out next year.
Eoin Colfer has to be my second but he's still a good author nonetheless, he wrote tons of books but if there was a book I had to pick, it would be the first Artemis Fowl, that book was amazing.
Pittacus Lore is my third. His series is amazing, even though its just one series(which is called Lorien Legacies) the books are just filled with action, suspense, and a touch of romance.
Anthony Horowitz would be my fourth, I've just read his books recently and I've got to say, he did a wonderful job. I almost put him as my third but since I just started I shouldn't really put him there... yet.