There were a couple of documentaries made about it.
Kicking Off The Rise and Fall of the Super League - 1 hour programme made by BBC
Super League: The War for Football - 4-part that I think was shown on AppleTV
Thanks for the response, but they don't tell us anything we didn't already know ( I haven't seen the Apple TV one but form what I've read it doesn't appear to cover any new ground?)
The New York times seems to have done further reporting having seen the contracts signed by the clubs.
I can't find anything that clearly reports on the timeline of events, the main players behind it and how it took shape, when clubs were invited and what they knew of it, leading to the calamitous announcement and subsequent withdrawal.
There is anecdotal stuff around Real and Juventus planning this for 3 years (although Real has been wanting a Super League for much longer than that).