Ancient Books

[「Ｚａ Ｗａｒｕｄｏ」]

What to do with them after reading? Do you sell them or are they usable in anything?

[Yograin]

You can sell them as far as I can tell but maybe you should wait with reading them until you are a member of the mages guild.

[Sotanaht]

They make good sacrifices to Itzpalt, if you ever end up worshipping that god. Since the read books all stack they don't take up too much space "just in case". He's one of only 3 gods where you can't easily mass-produce his sacrifices, the other two being Horome and Yevan. Be careful not to sacrifice more than 6 at a time though or you'll waste potential Piety.

If you're not going to do Itzpalt then yeah, just sell them

[CornBreadtm]

Save them and turn them into naughty books later when you learn the craft. You use those to learn enemy weaknesses.

[ＫＵＷＡＢＡＲＡ桑]

I used to sell them but I'm going to start saving them for Naughty Books. It's nice cosmetics to have them(either NB or Deciphered) on your bookshelf in your base library(or bedroom) in the meantime.