I'm a little conflicted about An Abundance of Katherines - I enjoyed the ride, but had several issues with the believability of several key elements. Central of these is the improbability of anyone, particularly a teenage boy, being both able to have nineteen relationships (albeit some very short-lived), all with girls named Katherine, and yet be so wholly clueless about appropriate human interactions that he closely abuts having an autism-spectrum disorder:
"Do you sometimes feel like a circle missing a piece?" his dad wondered.His parents might also have wanted to work on that a little.
"Daddy, I am not a circle. I am a boy."
And his dad's smile faded just a bit - the prodigy could read, but he could not see. And if only Colin had known he was missing a piece,that his inability to see himself in the story of the circle was an unfixable problem, he might have known that the rest of the world would catch up with him as time passed. To borrow from another story he memorized but didn't really get: if only he'd known that the story of the tortoise and the hare is about more than a tortoise and a hare, he might have saved himself considerable trouble.
The writing was in places very powerful - on the same page as the extract above, a young Colin is portrayed trying to interact with his peers in a way that made me cringe with the recollection of a similarly socially inept school mate. If only she'd had a Hassan - he lets Colin clearly know when he's veering off into the realm of the dull with a series of "not interesting" interjections whenever Colin pontificates his way into tedium.
I also found increasingly grating on its every encounter the heavy use of 'fug' (as in 'motherfugger' and 'what the fug..'), a word not addressed until midway through the novel, when I was heartily sick of it.
By the last third of the novel I was at the point where the use by Green of specifying gender when Colin and Hassan visited a woman in a retirement home jerked me out of the narrative as much as another 'fug' would have.
I'm quite pleased to have added several new words to my vocabulary, though I suspect it'll be some time before I can use abligurition or sillage, I also found the contemplation about the adult lives of gifted children interesting, though not new - borderline gifted at school myself (enough to get placed in the gifted stream, not enough to be started out there) I was surrounded by pushy-parented prodigies.
Colin has a fascination with anagrams I don't share, and though I suspect those who do enjoyed the sections they appeared in, I skipped over them along with the mathematical formulae that evolves through the text. This last section is also discussed in a mathematical epilogue - it was all way over my head, but there's also a link to a fairly accessible Slate article on actual research on relationship formulae, if you're interested.
Despite these aspects, there was much to enjoy in An Abundance of Katherines, from the premise to the character development and the bizarre but often believable world Green's built; that may be why I was particularly disappointed by the ending, which trailed off. However, I had a similar response to Green's YA novel Paper Towns, so perhaps this is common to his work. - Alex