I'm half way through it which has covered everyone's childhood, meeting up at a software company, and then going off to do their own games under the Id name, and finally the work of producing and releasing Doom.
Even though I lived through those times and I was doing some programming back then, I never really appreciated the breakthroughs that Carmack was responsible for. He INVENTED all the basic techniques used in 3D gaming today WITHOUT and had to optimize it for regular EGA and VGA without the benefit of any graphic processors.
People (mostly universities and production companies like LucasArts) were doing 3D but it was rendered 3D that took hours to render a few minutes of video. Carmack's incredible brilliance was figuring out was of making the PC (not a machine optimized for graphics) to render 3D in real-time.
I had no idea how much money these guys made in such a short time - and keep in mind this was SHAREWARE. They gave away the first episode FOR FREE and only expected 1% of the people who played it to buy the whole game for $40.
Castle Wolfenstein 3D was their first major money maker, and was making them an impressive $100K a month.
Doom, when first released, was bringing in an incredible $100K A DAY! And there was practically no overhead, and since they didn't use a publisher, they profited 90 cents on every dollar.