Authors selling books in Maine will need to register for a Retail Certificate (not Resale) and pay taxes on books sold.
The main page for info about the sales tax is at http://www.maine.gov/revenue/. The link for the application is http://www.maine.gov/revenue/forms/general/reg.pdf. If you sell more than $3,000 worth of books, you can apply for a RESALE certificate so you don’t pay sales tax when you print books.
You do not need to claim sales tax on books that have sold through Maine Authors Publishing (bookstores, Amazon, or MAP website). If you sell through a bookstore, you should get a copy of their resale certificate and you don’t need to pay tax on those sales.