Dear Aunt Debbie,
You make me look forward to my children's math education! In the meantime, we are forging ahead with Edward Eager with Eleanor, and rereading The Adventures of Isabel, In the Night Kitchen, and When Sophie Gets Angry -- Really, Really Angry... multiple times a day with Isabel. Her new favorite phrase: "Read't again!"
At the beginning of every semester, I ask my high school students to write me introductory letters, telling me a little bit about themselves and their history with reading and writing. I asked my 9th-graders specifically to name books they love, and as I read through them, I jotted down notes about the titles that came up most often.
The Harry Potter books were the hands-down favorite -- everyone has read them, and everyone adores them, no surprise. Those books have staying power. The Hunger Games trilogy wasn't far behind.
The third most-popular books mentioned were the Percy Jackson series, by Rick Riordan. You wrote about them briefly a little while ago, when we were talking about mythology. I think it's time I checked them out.
Two other series that came up often: Mortal Instruments, by Cassandra Clare, and The Sisters Grimm, by Michael Buckley. The description of the first book of Mortal Instruments ("the handsome Jace introduces fifteen-year-old Clary Fray to the world of the Shadowhunters, a secret cadre of warriors dedicated to driving demons out of our world....") doesn't fill me with a great desire to pick that one up, but the idea behind The Sisters Grimm seems promising: two young sisters, descendants of the Grimm Brothers, find out that they are fairy-tale detectives and need to solve mysteries in a world where the characters from fairy tales have come to life.
Finally, I was intrigued by the mention of The Agency series, by Y.S. Lee: Mary Quinn, orphan and thief in Victorian London, is taken in by a girls' school which turns out to be the cover for an all-female detective agency. Here's a more thorough take on the series from the blog Brown Paper. They sound similar in tone to the Sally Lockhart mysteries, though I'm not holding my breath that they're as good.
I'm sure you're far more familiar with all of these titles than I am. I'd be interested to hear your thoughts, both on these books in particular and on why series seem to have eclipsed stand-alone novels so completely in the hearts of teenagers.