Silent Hill: Book of Memories became an action RPG because of experiments, Tomm Hewlett, the game's producer, said in an interview on the PlayStation Blog.
"We really wanted to experiment with multiplayer," Hewlett said. "Survival horror is a very particular genre, but with PS Vita’s online capabilities, it just made sense to do multiplayer here. So we started to experiment with different gameplay styles … and through a long random assortment of events and demos, we came across a dungeon crawler, action/RPG thing which is really compelling with multiple players."
Hewlett goes on to discuss how the game adds action RPG elements like abilities and leveling while staying true to the franchise's survival horror roots. He also said that many of the game's 21 stages and seven environments are homages to themes in other Silent Hill games.