The Year of Secret Assignments by Jaclyn Moriarty

This book had an interesting format.  The entire story is told through letters written between students of rival high schools as part of a pen pal assignment.  Sometimes I would get a bit confused as to which character was writing to which other character, but I could just easily look back to remind myself who was "talking" to who.  This format made the book move along very quickly.  I was surprised at how detailed the story got with this letter format. The letter format also made it a quick read.  I enjoyed it.