The hype behind The Great Gatsby currently is due to the fact that it was just turned into a major motion picture. When the book was first written, it did not sell and F.Scott Fitzgerald died without knowing that his book would become a classic.
During World War II, the book gained in popularity. Now it is gaining in popularity again, partly due to the movie. I also think this is a book that speaks to a certain time of resistance to social change. During World War II this was a common topic of conversation, as it is now. I think this book will continue to ebb and flow in popularity as society deems it topical and relavant.