Non-fiction books aren't just about "transmitting great ideas" but also transmitting vast amounts of detail about more niche things. Take ancient history, for e

Non-fiction books aren't just about "transmitting great ideas" but also transmitting vast amounts of detail about more niche things. Take ancient history, for example: it is common for books run to many hundreds of pages, but that length was necessary to cover both political events and everyday life, to go over all the evidence a historian relies on to reconstruct the past, to treat disputes among experts, etc. You just aren't going to find the same amount of detail in a single place on blogs.