A couple of points in the talk stood out, I thought.
First — this was actually a response to a question at the end — Hooper commented that while he read Lewis for the first time in 1953, over the next ten years, he had a good deal of difficulty acquiring Lewis's books. There was a bookstore in Greensboro, North Carolina with which he had a standing order for any Lewis books they could turn up, but it took him a long time to acquire most of the Lewis oeuvre. (I now wish I had asked him how many Lewis books he owned by the time he met the author in 1963, just months before Lewis's death.)
A closely related matter was the chief theme of the talk: Hooper's prime concern in his early years of working for the Lewis estate was to keep some of Lewis's books from going out of print, and to bring the others back into print. I am not sure how many of Lewis's books were in print, either in the UK or the US, when Lewis died, but it would be a fraction of the number in print today. (Thanks to Hooper's editorial efforts there are Lord knows how many volumes of periodical pieces that Lewis had never collected in his lifetime.)
It's hard to believe that there was a time when C. S. Lewis books were scarce, when you couldn't track them down without great effort and great patience. (And I guess one of the prime justifications for Google's digitization project is to prevent anyone's books being so hard to find in the future.)
One last anecdote: I have claimed that Lewis's greatest book is his history of English literature in the sixteenth century — he took fifteen years to write it — which led me to smile when Hooper recalled a conversation he had with CSL's brother Warnie in the late 1960s. Warnie lifted a copy of that hefty volume, looked at it with some puzzlement, and said, "I don't suppose anyone has ever read this, do you?"