I don't have any real suggestions, but the two important Euclidean books were the Elements and the Data; the latter is about what exists, and the former is about the relations between what exists.

You're right that Plato was the first to write that there are non-mathematical relationships, and to try to formalize them, but what he meant by "non-mathematical" basically meant "non-geometric"; recall that we're talking about a few hundred years before the invention of algebra.

This laid the seed for Aristotle to formally declare that logic is its own discipline, rather than just the method used in geometry, and this is when we see these projects extend to everything, but no longer as axiomatic pursuits.