I already own The Maya by Micheal D. Coe and Stephen Houston, but I would like to know more about the political situation (what states/kingdoms existed, who ruled them, what wars happened - the book I have doesn't go into very much detail on this) on the Yucatan Peninsula in the late Postclassic, specifically information on the period between the formation of the Aztec Triple Alliance and the Spanish Conquest. (So I guess from 1428 - 1520s) Are there any good sources I could use? I understand information on this period is scarce, but anything related to the political situation would be helpful.
Your best bet would be The Political Geography of the Yucatan Maya by Ralph Roys. What he tries to do in that book is try to understand indigenous Yucatan right before the arrival of the Europeans, with an emphasis on the political situation, which is what you seem interested on.
Another good one that you may be interested in is Indian Background of Colonial Yucatan by Frances V. Scholes and Ralph Roys. This one is pays more attention to the way the Maya were seen by early Spanish commentators, but there is a section titled “What the Spanish Found in Yucatan” that you may want to explore.
Also a good one, yet lengthy, is Twin Tollans: Chichen Itza, Tula, and the Epiclassic to Early Postclassic Mesoamerican World, edited by Jeff Karl Kowalski and Cynthia Kristan-Graham. This is focuses on the time period just a bit before what you want but it may be a good background source to understand the late prehispanic history of the Yucatan Peninsula.
Finally, a good background source for the Postclassic period for all of Mesoamerica is The Postclassic Mesoamerican World by Francis Berdan and Michael Smith. This one is a foundational work to understand the period as a whole.