"6502 Assembly Language Subroutines" by Lance A. Leventhal & Winthrop Saville is a textbook published by McGraw-Hill Osborne in 1982. This book focuses on programming with the 6502 microprocessor, specifically using assembly language. It covers a range of topics related to programming, including general programming concepts, microprocessors, and assembly language. With 550 pages, this trade paperback is designed for adult education and further education levels, making it a valuable resource for those looking to expand their knowledge in the field of computer programming.