Lung's Golden Hours by Ernest Bramah
First published in 1923, re-issued in paperback by Ballantine in 1972 as part of Lin Carter's "Adult Fantasy" series. These are "long galleys", a fairly common format for paperbacks. Probably very few were issued for each title, and fewer were kept around (they are not easy to display or store properly.) Interestingly, the author's name is misspelled on the label.