Fablehaven: Secrets of the Dragon Sanctuary by Brandon Mull, 527 pages

"Two hidden artifacts have been found. Three more remain unrecovered. More preserves face destruction as the Society of the Evening Star relentlessly pursues new talismans. Reading in Patton's Journal of Secrets, Kendra learns the location of the key to a vault housing one of the artifacts. In order to retrieve it, the Knights of the Dawn must enter a death trap - a dragon sanctuary called Wyrmroost. The mission cannot proceed without stealing a sacred object zealously guarded by the centaurs. Anybody seen Seth?" -Book Jacket

Fablehaven is series that gets better and better with each book. Seth has grown up a lot over the course of four books. He is still reckless at times, but it seems to be more of a calculated recklessness. He seems to weigh his decisions more now rather than just charging full speed ahead. I try not to write too many spoilers so I'll just say that I loved the knapsack, I was saddened (and suprised) by the betrayal - although it was a great twist, I loved that Kendra and Seth discovered new powers when they held hands, I think that they will have to unite to defeat the Sphinx and I can't wait to read the last book.