Read everything you can get your hands on: library books, books you love, books you hate, newspapers, encyclopedias, backs of cereal boxes, cookbooks, books that want to eat you.
A writer should read while he is relaxed because that is when the stuff he's reading sinks most deeply into his mind; furthermore, reading should be his primary form of relaxation, not skiing or tap dancing or fishing or building model trains or watching television, but reading.
No novelist can expect to reap harvest after harvest of fresh ideas from his subconscious if he is not constantly fertilizing his subconscious with reams of other writer’ fiction and nonfiction. With every novel you read, thousands of facts, characters, images, narrative techniques, and plot twists are stored in your subconscious, thereafter constantly interacting below the level of awareness. When bits of this input jell and surface, they are usually in an original arrangement that bears no resemblance whatsoever to the books from which they came.
Do you have a list of books from which you are reading?