Fallout: Equestria - Letters to Celestia is an in progress [Equestria|Fallout Equestria] side fic written by AlmanacPony. It has Eight chapters )not including an Intro and Foreward) and is currently 124,096 words as of 6th March 2017. Set years before the first Fallout Equestria fic by Kkat, it is written from the first person perspective of Tome Tale, as though he were writing it himself. Professed in the Intro to be a form of diary written like a story, each chapter begins with 'Dear Princess Celestia...' and reads with many personal thoughts and feelings from Tomes perspective.
Read it on FimFiction.