In "An Aviator's Field Guide to Middle-Altitude Flying" author Jason Blair shares his experience in a variety of piston twin-engine aircraft regularly used to fly in middle-altitudes, typically between 10,000 MSL and 25,000 MSL. This book describes major phases of flight and considerations that pilots who operate aircraft capable of flight at these altitudes may find useful as they develop their skills and seek tips and methods possibly missed in their initial training. This is the author's result of years of instructing and taking notes previously passed on to his own students, now compiled and shared with the broader aviation community.The pilot owner/operator of aircraft capable of flying above 10,000 MSL, up to altitudes in Flight Level 20s, may have had limited training that addresses this type of operation beyond basic aircraft systems and performance training. For these pilots, Jason Blair's notes and suggestions help to expand technique more broadly into "middle-altitude" flight operation.