@jeffmartins@masto.ai
A convincing argument could be made either way as to whether Zen/Chan is a religion or not. 😉 I don't think I actually view it that way, though there are plenty who do. There isn't a required belief system or ontology to adopt, which I think of as a necessary component to qualify as a religion (nor anything supernatural, another biggie).

To get a good introduction to the basics, I"d recommend Steve Hagen's "Buddhism Plain and Simple." Hagen is a contemporary Zen teacher and founder of a Zen center in Minneapolis.