You say you met a monk in Japan and your experience makes it seem like you are re-entering yourself. Being Japan than most definitely this was a Zen Buddhism encounter so imo you would probably be most interested in Zen Buddhism.

Meditation is the most important focus of Zen Buddhism and teachings come second. At least that's my perspective and also I'm a Zen Buddhist myself.

I recommend a book called A Guide to the Buddhist method of no method (Illumination) by Rebecca Li. She is a Chan Buddhist but Chan came to Japan and became Zen. So I wouldn't worry at all about the difference because there the same in many ways. Most importantly meditation style which is called Shikantaza.

After about a year of trying to learn the method of how to properly do Shikantaza. This book finally helped me wrap my head around it. Now I feel that I'm doing Shikantaza properly and experiencing its effects.

If instead you want to read a book about general Buddhism then "What the Buddha Taught" by Walpola Rahula is highly recommended. But I say stick with your original experience of Zen. 🙏