Despite his relatively short, clean career record, President Obama could have been praised or blamed for several things he actually did before taking office. Instead, Klein chose to call him an introvert, which Klein didn't even seem to understand is a permanent physical trait, but seems to think is a character defect.
I think this was a sneaky move, an effort to sell Obama's opponents a book that appears to blame Obama for having inherited a likable physical trait. I'd even call it a cheat, because Regnery's target audience expected a hostile biography of Obama to trace his political deal-cutting or policy reversals, rather than speculating about his neurological profile. And I'll throw in that it's unconvincing, because Klein presents no evidence of Obama acting like an introvert--only of his acting like a young man, a gentleman, or both.