From the B&N Review:
JM: Your books come out at a prodigious rate, but from what you say about the struggles of writing I'd imagine there's a lot of drafts and so on that prove unfruitful. How much writing do you do that doesn't see the light of publication?--Czobit
PR: There are a lot of drafts. I don't seem any longer to make false starts and write 125 pages, and have to throw it all away -- although I did earlier in my career. Sometimes I do make a false start of 25 or 50 pages and put it away; a year or two later, I look at it and I see what was wrong, then scrap most of it and start again. But by and large, it's drafts. I write drafts and drafts. Let's say that, on average, I write between 5 and 7 drafts of a book, trying to bring it to life, really. When I get to the point where I can't do anything more, I consider myself done.
JM: Have you begun another book?
PR: I've finished another book.
JM: Can you tell us anything about it, or would you rather not?
PR: I'm going to get an A in the course, aren't I?
JM: Gold star.
PR: I don't want to talk about it. It will just confuse the conversation about Indignation. But I just recently finished a book, also a short book, which will come out next September.