Crank is a novel written in verse, so it is an extremely quick read despite its 537 pages. I ended up picking it up for my eReader when it was on sale, and while I enjoyed it, I think it's a hard book to review in a lot of ways. There were some pretty horrifying and sad scenes, and Kristina could also be a frustrating narrator, but I finished the book in 1-2 days, so I guess it's clear that I enjoyed reading it despite my issues.
I periodically found it a bit hard to follow, but was usually to pick things back up again after rereading a couple of lines. Reading it on the eReader was a little weird from time to time - I had the font size as small as it would go, but still had to turn it sometimes so that the lines would display the way they were originally intended. I think a paperback copy of this would probably be easiest to read, but I generally wasn't too inconvenienced by the formatting issues because they were usually pretty easy to recognize and sort out quickly.
I didn't really understand the alter-ego stuff with Kristina/Bree, but I eventually just accepted it. Bree almost seemed like a coping mechanism for Kristina at times, a way to distance her old life from the new. I found that interesting, but also sad. Knowing Crank is loosely based off Hopkins' daughter's experiences really makes parts of the book hit home, and Kristina's decline is swift and disturbing. I am interested in continuing with the series, but Crank was a pretty heavy read despite being quick, so I may wait for a bit before continuing.