The annual Tucson festival of books is the place to be, but if you miss it, there is always the next year. Meet the authors, join the authors' forums, and buy the books.
There is an online e-edition of the Tucson Festival of Books guide that has all the information you will need about the authors, events, exhibitors, food and so much more.
Parking is at a premium so go early. It is all free to do. Funds made from food, book, and merchandise sales pay for it all.