They have a few options for creating books, including PDF upload; a couple of high-power Adobe applications mostly suited to top-quality photo books; and Blurb BookSmart, a dedicated DTP program designed to interface with Blurb's system. I went for BookSmart. You register to download it, create your book, then upload the book direct from the program.
|BookSmart - edit mode|
|BookSmart - preview mode|
|BookSmart - image organiser launched|
My proof copy took a week (ordered 16th November, arrived 22nd November); the quoted ETA was 3rd December, but I assume this is a Mr Scott worst-case estimate to cover them legally, Once it's in transit, you can follow the FedEx delivery trail online, and so know what day it'll arrive, which is a nice touch.
Note that you won't get into any kind of personal interaction with Blurb; any help you might want is conducted through their forum page, and that doesn't go beyond nuts-and-bolts of using the software and the system.
This is actually a significant point. Self-publishing does need a large toolkit of skills beyond writing the stuff: for instance, a modicum of aesthetics about layout, readiness to learn how to use various software, ability to manipulate photos and other graphics (if you're doing your own artwork), organising ISBNs (both the number and creating the barcode), and so on. That's not to mention your responsibilities - and I've found these horribly good at keeping me awake at night - for areas such as copyright and photo permissions.
What you upload is what you get. Blurb won't talk you through the creative process, do your ISBN, or spot any proofreading or legal problems for you. But if you have those skills, and are 100% confident about exactly what you want printed, Blurb will do their side of the job quickly and outstandingly well.