D. Keith Robinson on Being Introverted:

I really enjoy, and require, alone time. I'm classically introverted: interaction with people drains me. Even talking intently to one person drains me. I need to prepare for being social

Sums it up nicely. It's not that introverts like people any less. Social interaction is just a complex process, often many processes at once. Every conversation is a flood of information in the form of facial expressions, body language, inflection and subtext. 

Also: The Pastry Box Project