Okay, let's just get this out there, if we're going to Apocrypha, it'd be a damn shame not to have a huge load of new books in, and maybe a few of the old favorites that didn't make it into Skyrim. Hell, some of the old favorites would probably be easy to find on Solstheim in the first place because of the Dunmer.

Anyway, what kind of books would you like to see? I'd like to see a lot of "weird lore" books return from Morrowind, like the Lessons of Vivec, and to find a lot of books on old Dragonborn like Tiber Septim and Alessia in Apocrypha, to keep with the theme. I'd like books about the travels of the Dunmer from Vvardenfell to Solstheim, treatises on Morrowind and Solstheim wildlife, Telvanni journals about magical research and a secret lost chapter to Crassius Curio's plays.

A historical account of the past two hundred years.
The founding of the College of Whispers and the Synod and what they represent.
What happened in the aftermath of Umbriel.
More information on the Reman dynasty.

New authors with new works of fiction too. In the past two centuries there must have been more people like Waughin Jart.

We have very, very little information on the past two hundred years in Skyrim and it bugged me since the start since I expected this would be the perfect chance to introduce new books.
Its a little odd to still have 80% the same books as in Morrowind and Oblivion, people just dont stop writing and keep reprinting what their ancestors wrote like that.

Dawnguard adds some excellent new books and I hope Dragonborn will do too.