Roger Kastel, best known to me for his iconic painting for
Jaws (see image below) did this wraparound cover for a paperback edition
The Royal Box by Frances Parkinson Keyes (1885-1970) in 1968). It is gorgeous and huge, 30+" by 26+". It was kept with butcher paper pressed against it, much of which stuck to the paint. I did some careful restoration and got most of the paper off without harming the painting. I have a copy of the cover below.
Thanks to Daniel Perkin, Will K., Grace Kastel (indirectly) and Kastel Art for finding and confirming the artist for me. The Roger Kastel has a website rogerkastel.com.
After removing the butcher paper altogether, I found a name and address stamp on the back with Roger Kastel's name and address.