Genre fiction

What is it about genre fiction? And to dig deeper to its essence: what is it about reading all the books by the same author of genre fiction? It's about knowing what you'll get and not minding, in fact, counting on, getting that same reliable mixture of pleasing ingredients.
Real literature, I'm sure, isn't done this way. Those engaged in it are always experimenting with new forms and subjects, growing as artists. But what I like to read are writers who are happily, or at least profitably, digging themselves into the rut of their success. And I will happily follow them there.
James Lee Burke, for example, will write another Dave Robicheau novel about the recovering alcoholic, social justice Catholic detective who rides roughrod through the lives of the Louisiana rich and powerful. A conflicted hero, often given to self-loathing, occasionally to insane violence. Burke manages, I think, to create literature from within this genre, but others would disagree. What do you think?