For anyone not familiar with this series, it is perhaps the best documentary ever focusing on the silent era, if not the best certainly on a very short list. There are interviews from dozens of notables from the silent era. I believe Brownlow had been filming these since the late 50s so he was able to include some who had passed away by the time the series was released in 1980. The number and quality of clips from silents both celebrated and obscure that are included is pretty amazing.
I remember watching this in 1980, and I believe it was repeated on PBS at some later time, which is when I recorded my blurry VHS copies. Each show is organized around a theme, I can't remember all of them but they include Comedy, Stunts, Special Effects, Early Sound, Cinematography, etc. My favorites were Comedy, Special Effects, and Stunts (lots of amazing stuff which wouldn't even be attempted on any set with an insurance policy today). Also, despite the title, there is a episode devoted to foreign silents as well.
In addition, I found the brief opening credits sequence to be the most thrilling I have ever seen, movies, TV, anything.
Brownlow's book The Parade's Gone By (1968) is pretty much a blueprint to the series. Although it isn't a point by point companion piece, a lot of the material in the book winds up being used for the series. I would recommend it to anyone interested in the history of film, silent or otherwise, as indispensable. It appears to be in print.
I believe the full series has been available on VHS for some time, but I am looking more forward to a DVD release of it (whatever region) as much as anything I can think of.