Below, I will respond as a monk of the Soto sect.
Most of what is commonly referred to as “Buddhism” is probably a story about “Buddhist conventions” where things like secular and historical “customs” are accumulated. It's about the history of temples, the origin of gods and Buddhas, and stories about relationships with foreign religions...
Is the “Buddhism” the questioner wants to know about such conventional knowledge, or is it an anthropological teaching handed down from the Buddha? If it's the former, various books have been on the market in the past and now, so I think you can get some knowledge if you buy something, but the latter is probably what you originally wanted.
To be honest, this is a part where neither I nor I can clearly present “this is it,” and it is often a problem (^_^;
Certainly, you can study with books and the like based on classical materials, but that's not enough... I think he is a “teacher” who can teach everything other than himself regardless of age or gender, and he pursues every day with many people he is involved with, and he repeatedly shapes the construction and destruction of theories over the course of a lifetime.
Also, we monks have “mentors of monks who are directly connected” as close people, but there aren't many mentors close to the general public who can establish such relationships... it's a troubling problem...
I am ↓
・Buddhism learned from books such as sutras and sutras is an “index (headline) of Buddhism”
・Learning Buddhism through relationships with others is the “main content (content) of Buddhism”
I think so.
Also, depending on the stance on this side of learning, what falls at any cost is “learning.” It depends on how you want to “learn” from that person or that thing, doesn't it? Of course, the opposite is also true.
By the way, even now that I'm groaning and answering...
I think it's an important Buddhist practice (^o^)