Publisher gets irritable when first deadline passes. Publisher gets angry and sets another deadline. Writer tries to do some writing, and misses said deadline. Writer eventually finishes book. Publisher is happy, and pays writer copious amounts of money.
Writer is mobbed by scores of marauding fans armed to the teeth with autograph books.
Don't tell anyone about it. If anyone asks what you are doing, say you are playing one of those computer games that is so complicated, if you leave it now, you'll never complete it, ever. Write the book, without pressure of deadlines or death threats from irritable publishers. Writer goes to lots of parties, and forgets about nasty Publisher. Writer magically makes all the deadlines.