One of my favorite things to do each summer is read as many books as I can enjoy (which is usually a considerable amount). I like to read to relax, to be entertained, to get my mind off math, and to learn. I've been reading the Sookie Stackhouse "southern vampire" books and have been enjoying them in a fluff sort of way. They are easy to read, quick paced, a bit romantic, and very entertaining.
Here is my summer reading list from most recently read to read just after graduation - copied from goodreads.com - ignore the stars. I enjoyed Poison Study and Hourglass Door the most off of this list.