The work of a painter supposedly becomes more highly valued after the artist dies. That isn't what normally happens with writers, however. There are a few like Mark Twain and Ernest Hemingway who, esteemed in their lifetimes, continue to be esteemed after their deaths. But most writers tend to fade in reputation after their deaths. Their books go out of print. Libraries discard their books to make room for newer ones. Only a gradually declining number of readers remember them at all. That is, unless something magic happens.
Susan Hill wrote this a few years ago about novelist Iris Murdoch: "At present, her reputation is in the decline to near-oblivion that customarily follows the death of an author. It is the time -- and it can last anything from five to fifty years -- when novels sink and are forgotten as the reading world moves on, before someone plunges an arm into the depths and pills up first one then another -- and so begins the slow process of reassessment." Of course, this reassessment occurs only for the fortunate few novels by the fortunate few authors. Most writers, once forgotten, stay forgotten.
The magic can happen in a variety of ways. A biographer or literary critic may write an influential book or article that revives interest in a author. A publisher may decide to reissue some old books, perhaps encouraged by the expiration of the copyrights. A film producer may choose to adapt an old novel for a movie, which makes people want to read the novel itself.
The latter is what happened in the early 1980s when British television turned the Evelyn Waugh novel Brideshead Revisited into a successful 11-part miniseries. Soon people wanted to read the 1945 novel they may have never even heard of before. Other Waugh novels also sold better than they had in decades.
As an example of how just one person can succeed in reviving interest in a forgotten author, I give you Tim Page. The former Washington Post music critic took an unusual interest in Dawn Powell, a novelist popular in the 1930s and 1940s, but ignored after her death in 1965. In the 1990s, Page wrote Powell's biography, collected her diaries and letters into books, and wrote introductions for a number of new editions of Powell's books. Powell had grown up in an area of Ohio very close to where I had lived for decades, yet I had never heard of her until Page brought her back to public attention. When I met him at a book fair in Wooster, Ohio, I shook his hand and thanked him for reviving the memory of a significant American writer. Sadly, Powell seems to have faded into obscurity again in the past 15 or 20 years.
Herman Melville, mostly ignored during his life, became famous years after his death. He is among the very few writers whose work became more highly valued after their deaths. There is just no way of knowing which writers will stand the test of time and which won't.