In a video I saw recently, the guy in it suggested [1] reading old books about earlier versions of DirectX from the late 90's and early 2000's, around DirectX v

In a video I saw recently, the guy in it suggested [1] reading old books about earlier versions of DirectX from the late 90's and early 2000's, around DirectX version 9, even though one does not want to ever use DirectX for the reason that most graphics engines are built on the concepts of these versions of DirectX he said. [1]: https://youtube.com/watch?v=06zp5GMe2rI&t=4m11s https://youtube.com/watch?v=06zp5GMe2rI&t=4m11s