Reddit reviews An Illustrated Dictionary of the Gods and Symbols of Ancient Mexico and the Maya

I've always found the core concepts found in Aztec religious thought and philosophy to be fascinating. A really great post, OP.

For those interested, here is an accessible, fairly inclusive introductory book that I own that covers not only religion and philosophy but also how those core beliefs applied practically to and shaped matters of war, trade, education, politics, and so on. It also includes splashes of Mayan thought, and touches on the pre-Aztec societies that were later incorporated into the Aztec Empire.

Ahhuatl's suggestions are great, and the Florentine Codex (especially Book 1) is pretty much your authoritative source. Leon-Portilla is another great resource and you may want to check out his Aztec Thought and Culture if you ever want a scholarly look at the philosophy of Aztec religion.

If you're looking for the myths themselves though, you may want to check out Taube and Miller's Illustrated Dictionary of the Gods and Symbols of Ancient Mexico and the Maya. It is a dictionary/encyclopedia though, so it may be kind of dry. Carrasco's Daily Life of the Aztecs doesn't directly tell the myths but does feature large passages on important rituals (and is just a good book overall).