The front cover says it all, "How to Load, Operate, Disassemble and Assemble American, British, Russian, German, Italian, Japanese and Other Small Arms"
Admittedly the 2 dollar sticker price on the front cover was a bit stiff at the time for a paper back. According to the CPI inflation calculator that would be $ 26.60 in 2013. Despite the price, I suspect that the book was a good seller, the copy pictured here is the Fourth printing from April 1944. The first printing was in December 1943.
This heavily illustrated book includes evaluations and field strip instructions for many military small arms of the day, including Schmiesser Submachine Gun and the U.S. Rocket Lancher, A. T. M1 aka the Bazooka.
This book after the War evolved into a fine book in it's own right, "Small Arms of the World"