Apples and oranges. Chandler — although a good writer — was genre. Grapes of Wrath, on the other hand, was pretty much general fiction aimed at “every man.” Today, the general fiction list of most publishers is very sophisticated and aimed at the educated urban reader. And yes, there are exceptions.
No Grapes of Wrath had a target audience, people who are interested in poor share croppers, there really never has been and never will be a “general fiction” list, all that is is books they can’t slap a convenient label on. The modern “general fiction” list is just as broad as ever, from the stupid criminal stories of Elmore Leonard and his clones (and BTW these guys are very prolific writer and get a lot of their books turned to movies, they have a clear every man appeal) to whatever the hell it is John Updike writes. There really aren’t exceptions, because there is no rule. There are plenty of books for reasonable prices that the every man can read if he so choses.