If you wanted to enter politics and you could only choose one Objectivist book to study which book would that be and why?
If you were going to enter any field that deals with ideas and values, you’d be wise to acquire an understanding of Objectivism from the standard sources.
Something tells me that you’re really asking if the Objectivist literature has any advice on how to conduct a political career. It doesn’t. The field is wide open for you to discover such advice and, if you wish, share it.