POPULAR SERIES ROUND-UP
The very best way to find out what is popular in your town is to ask kids and teens, also ask the school librarian.
For other ideas, take a look at the unscientific survey results (combined with the more scientific combing through MORE multiple holds data) from July/August 2010 in the Keeping Up With Kids Blog:
Kids:
Teens:
Finally, here are some places to keep track of national trends: