To see if the motion picture rights are available for a book, contact the publishing house and ask for the subsidiary rights department. In most cases, they will refer you to the author’s lawyer or agent. In some cases, however, the publishing company will own the rights in which case, you can speak with them directly. If the rights are available, you will negotiate with the rights holder (or their representative) the terms of the option/purchase agreement. If the rights are not available, feel free to ask when the current option agreement expires and be sure to recontact the rights holder at that time.