The Eight-cent Prexie
Fourth class book rate plus insurance
Prior to 1949 books over a certain number of pages could be sent under the book rate, which was three cents per pound from July 1, 1942 until January 1, 1949. Minimum insurance was five cents from April 15, 1925 to March 26, 1944.
Ruth Webb Lee published handbooks on Victorian pattern glass and valentines during the 1930's and 1940's. These weighed more than four ounces, so this mailing was quite likely to have been done under the book rate rather than as double third class. The combination of postage and insurance dates it from 1942 to early 1944.