Tracts are an interesting mechanism/form to disseminate ideas and information, but are seemingly less common in today’s publishing world. Tracts can be on anything from philosophy to religion to politics, and influential tracts have been written through time, such as Common Sense by Thomas Paine. They are written to be as accessible, short, and straightforward as possible, and that is one of the greatest strengths of the form. You could finish one in a single sitting.
I just came out with a tract, this one on metaphysics, and it’s called Equivalence. You can find it on my author page: https://www.amazon.com/Phoenix/e/B00QEL41LS
Check it out!