Moments before I wasted my money on a book about writing well, Amazon suggested that I also buy a book on writing a lot. And since Amazon would never recommend a book that I didn't really need, I bought it.
The book is called How To Write a Lot: A Practical Guide to Productive Academic Writing. It's by a psychologist named Paul Silvia. It's cheap. It's short. It's not bad. If you really have a hard time getting writing done, it might be worth your money.
The book's fundamental message, though, is one that you've probably heard before: The secret to writing a lot is to schedule writing time and to stick to that schedule. You can start with a few hours a week, preferably spread over several days. But make a schedule and stick to it. That's it.
Philosophers will want to skip some sections. Silvia explicitly wrote the book for psychologists. There's a whole chapter on writing papers in the Introduction–Methodology–Results–Discussion format that dominates psychology articles. Annoyingly, the publisher describes the book as "[d]rawing examples from [Silvia's] own field of psychology," rather than being for psychologists.
Silvia's adopts an informal, humorous tone, which makes the book rather quotable:
"Finding time is a destructive way of thinking about writing. Never say this again. Instead of finding time to write, allot time to write."
"Like businesspeople, academics enjoy talking about goals. Some academics are so enamored of goals, initiatives, and strategic plans that they become deans and provosts."
"I assume that each paper I submit will be rejected. It's the only rational conclusion, and my faith in rationality is supported by the amount of rejections I receive."
"Rejections are like a sales tax on publications. The more papers you publish, the more rejections you receive."
"A writing schedule brings balance to your life.... Is academic writing more important than spending time with your family and friends, petting the dog, and drinking coffee? A dog unpetted is a sad dog; a cup of coffee forsaken is caffeine lost forever."