According to the Elder Scrolls wiki page http://elderscrolls.wikia.com/wiki/The_Lusty_Argonian_Maid , if you scroll down to Appearances, the Lusty Argonian Maid book makes an appearance in the Elder Scrolls Online. This book was written by Crassius Curio in the Third Era. And in the setting of the Elder Scrolls Online, Crassius Curio isn't even alive yet.
Why?