We have a stable of fine books now available here right on Paizo.com.
Tribes of Everglow, indepth lore of the tribes of ponies that inhabit Everglow, including the previously unmentioned but entirely un-statted Tribe of Bones.
Forgotten Past, discovering what came before the ponies, and what marks they've left behind, to say nothing of new options for players and GMs alike!
Princess Luminace's Guide to the Pony Pantheon, learn more about the divine presences that watch over ponykind, for good or ill. We also cover the luminous dragons and pony satyrs as player options!
Griffons of Everglow, while dwarves rule the undermountains, the griffons control the space above. Looking down at the ponykind, they have a history all their own.