I got this book ages ago, like many people, because I thought the list structure sounded cool - and it is. The ‘mark’ thing was kind of cute, and the music theme throughout had its moments. But it is largely plotless and I had no sense of time while reading it. There is no character development, or maybe even negative development, and I don’t have much hope for Darren at the end. I don’t doubt that his changing family situation is very hard, but he is just so nasty to the people around him and I found it hard to get through. If he wasn’t so shallow and judgemental, he might have more friends. Maybe that’s the point, I don’t know. 
It’s also classic MPDG trope - Darren just wants the weird girl to fix him and also become less weird (ie grow her hair, wear colour and take her piercings out), never mind the very real problems Zoey is probably facing off the page (she is only on a few of them anyway). Rachel also deserves to get angry at him.
Plus, he keeps saying he’s a vegetarian, but he eats fish. Maybe that shouldn’t bother me as much as it does.
I do want to visit Chicago, though.