Next to Solid in Short (which is more for business people), Digita is also working on a webseries to explain the fundamentals of Solid from a technical perspective.
Currently, we have uploaded two videos already and are working on several more.
Solid Tech Talk E1: The building blocks of Solid
Solid Tech Talk E2: A Solid pod: a vault and a database
Solid Tech Talk E3: Levels of interoperability