While roving the Internet today, I came across this webpage, which contains a lot of good info about This Rough Magic. It's part of a database on 20th century American bestsellers compiled by Library Science students at the University of Illinois. One thing I had never seen before was this newspaper ad that ran in the New York Times in 1964 when This Rough Magic was first published.
Were hardcovers really only $4.95 in 1964? Wow.