If I understand you correctly, there's no need for a separate library, LibStub is enough.
Lua Code:
-- myaddondata.lua
local data = LibStub:NewLibrary("MyAddonData-1", 1)
if not data then return end
-- fill it ...
Lua Code:
-- myaddon.lua, or someoneelsesaddon.lua, that wants to use myaddondata
local data = LibStub:GetLibrary("MyAddonData-1")