I already wrote it

My latest Astral Weeks column is a review of Charles Yu's excellent new novel How to Live Safely in a Science Fictional Universe. Here's a bit from the book:

Apparently, I'm going to write this book, which appears to be, as far as I can tell, part engineering field manual and part autobiography. Or rather, I already wrote it. Now I just have to write it, which is to say, I have to get to the point in time when I will have written it, and then travel back in time to get shot and then give it to myself, so I can write it. Which all makes sense to me, except for one thing: why the hell would I want to do any of that?