1984, George Orwell For SURE!!! Really really loved reading that book. A close second would have to be DUNE by Frank Hubert.
its so sad that you see people are becoming less in study of books today. for an example,people like to watch the harry potter film (2 hours),and ignore from reading its book that take their time of 1 month. time is been the main reason which make people prefer movie instead of reading books. i was an author and i know this way...
i also have read Sidney Sheldon.this is one of the best book book i ever read. you mentioned at right point !
My favorite book is by Russian writer Dostoevsky- Crime and Punishment it's classics, and classics will never die I reread it hundred times