Stephen King does it often.
Apparently, Wodehouse does it too: "He envied fellows like Gertrude's cousin, Ambrose Tennyson. Ambrose was a novelist, and a letter like this would probably have been pie to him." ~P.G.W. The Luck of the Bodkins
Novelists as characters.
I've never done written a novelist character myself, partly because I think that other fantabulous authors have done this meta-move with great distinction. King, definitely. Who can touch Misery or The Dark Half for writer-torture? Michael Chabon with Wonder Boys is the literary equivalent. (Read: workshops! Augh!)
There are hundreds of examples that I could point to with writers writing about writers. I think the reason for the existance of such a line-up is obvious: Write What You Know. Writers understand the struggles of sitting down at the computer/typewriter/page. Plus there is that extra bit of getting to talk about writing in writing--which, aside from writing, is what writers do.
We're kind of boring in that sense.
There's the additional bonus in that there's very little research. If your main character is a chef, you might have to go out and research the lingo. Not so when a novelist makes a novelist character. We already know "WIP" "galley" "ARC" and "How Advances Work." We understand what a ridiculous word count is. The jokes are inside and we get them.
Then there's the audience. You know who reads the most books? Give you one guess.
So of course I'll pick up a novel called How I Became A Famous Novelist (by Steve Hely). Or An Arsonist's Guide to Writers' Homes in New England (by Brock Clarke). It's like par for the course. The audience is built in.
How about you guys? Written about writers recently? Read a good book about writerly characters?