If you want to make sure that B.J. Novak signs your copy of his new book, “One More Thing: Stories and Other Stories,” get to Harvard Square early on Monday. Harvard Book Store — which is hosting the sold-out reading for Newton-bred Novak at the Brattle Theatre on Monday night — is also running a signing with the author from 12:30 to 1:30 p.m. Please make note that there are some rules. Novak won’t have time to personalize books, and you must have proof that you purchased your copy at Harvard Book Store. He will not sign anything other than the book, he will not pose for photos with you, and you may not look him directly in the eye. (Kidding about that last part.) There will be a staffer at the store to take photos while he signs for you. Actor-writer-producer Novak, who went to Newton South, is best known for his work on “The Office” and for collaborating with another hometowner, Mindy Kaling.