I gave this four stars initially. Then I went to write down a few notes on the topics and themes in this book, and come to think of it, I'm changing it to five.

The book doesn't feel dramatically groundbreaking or exhilarating. Yet there's a lot going on, the protagonist is quite interesting, and especially the titular theme - pattern recognition - is explored in depth and from various angles. Yet it's done in a "Gibsonian" manner: it's never explicitly rammed down your throat with tedious explanations. Plot happens, characters think, it's up to you to catch on.

Questions about art, fandom, and commercialization, and the internet are woven through the story as well. (The book is set in 2002 and was published in 2003, so the internet back then was something completely different than it is now.)

Also, I think the only reason this is tagged 'cyberpunk' and 'sci-fi' is because it's Gibson and people tagged it without thinking.
It absolutely isn't cyberpunk in any way; and I say it isn't sci-fi, either. You could possibly argue it's one of those set in "Next Sunday AD", like for instance Doctorow's Little Brother, but I'd say even that doesn't hold water here.