I was thwarted by Adobe Digital Editions.
Clearly Adobe don't want me to read this book. Or perhaps it's Penguin Books.
Google send you a .acsm file, which Adobe Digital Editions trades for the .epub you actually purchased, after doing the DRM thing. In my case, the DRM step didn't work, no matter which way I did it. I got a refund. It'd be one thing if I got a locked up .epub, I could just remove the DRM, but this file is useless.
And since I'm a nice guy, I emailed Stross and told him that I'm going to either download an ebook copy illegally, or just purchase the book used when the price drops.
Stross wrote me back:
> You tried; that's fine by me! Meanwhile, I probably don't need to tell you how much I detest DRM.
So there you go.