If you're asking where the actual bookstore itself is, it's the location labeled "BOOKSTORE" in Whitehaven. The quest begins after you ask the apparently prudish owner of the bookstore why she stocks the terribly obscene Art of Paine II, and her shifty response makes you think something strange is going on. Progress it by assigning a valid girl to the bookstore through her Jobs & Titles menu, under Stores.
It's available right from day 1, so if you're desperate to see the complete introduction text, you can just create a throwaway character and visit the Bookstore.