Persona 3 FES: Alternative Heart is the official novelization of Persona 3 FES.

It consists primarily of short stories touching on the themes of day-to-day life of the main cast of the games. Topics covered are Yosuke Hanamura not quite being used to living in the countryside yet, the fact that good friends like Yukiko Amagi and Chie Satonaka can still be awkward in some respects with each other, and Nanako Dojima worrying over her busy father. (Source: Megami Tensei Wiki)

It is an original story taking place during the Persona 4 storyline shortly after Yukiko Amagi's rescue. The story is primarily focused on Yukiko, Yosuke Hanamura, and Chie Satonaka as they enter the television world without the protagonist, who is written out of the scenario by texting the others he won't be able to make it that afternoon. Yosuke, instead, takes the lead role in this story. The premise is largely about him entering a different television than usual, drawn by a mysterious voice and the familiar figure of Saki Konishi.