Padmé Amidala is a human female of Naboo, elected Queen as a teenager and later her planet's Senator. She was introduced in Star Wars: Episode I The Phantom Menace (1999) and played by Natalie Portman.
The films underserve her; the books do not
Episodes II and III reduce a working head of state to a romantic subplot and then kill her on screen of a cause the film refuses to name. Prose has spent twenty years repairing this, and it is one of the clearest cases of the publishing programme correcting the movies rather than merely servicing them.
Queen's Shadow and after
E. K. Johnston's Queen's Shadow (Disney–Lucasfilm Press, 2019) and its sequels are the essential run: they take the handmaidens seriously as a political apparatus, treat the transition from monarch to senator as a real professional problem, and give Padmé colleagues instead of admirers. They are marketed as young-adult books and are better than most of the adult line.
The Delegation of Two Thousand
Her most important act is a piece of paperwork. In the last days of the Republic she is among the senators who petition the Chancellor to relinquish emergency powers — a scene largely cut from Revenge of the Sith and preserved in the novelisation and comics. It is the correct thing to do, done in the correct way, and it fails completely. That is the prequel era in one gesture.
Reading note
She is also the reason the saga has a second and third act at all. Read her material before the sequel-era books; the family it produces makes more sense afterwards.