In the end, Colin pretty much rides off into the sunset with Lindsey and Hassan. But before you go all eye-rolling on us, check out the last line in the book: "And he was feeling not-unique in the very best possible way" (epil.32). That doesn't sound so sappy now, does it? Colin's feeling at the end of the book is one of happiness, but also of realism. He finally gets it—he doesn't have to be a whiz kid who has eureka moments and spits out not-so-interesting-factoids everywhere he goes, nor does he have to be social and make friends with people he doesn't want to.
For most of the book, he's gone around thinking he was just some guy who nobody liked, who always gets dumped by Katherines. But in the end, he's figured out that he can be whoever he wants to be. His world is full of possibilities—he just has to figure out what he wants to make of it.