Pocket Guide to the Empire 4th/5th/Whatever-eth they're at by now Edition.
I want to know what happens in between the 160 years between the novels and Skyrim.
If not that then a little dragon statue, like the Ordinator from the Morrowind C.E.
Detailled Map of Skyrim is third, unless a map of Skyrim is included with the game already. (Like Morrowind and Oblivion)