The Avro Lancaster heavy bomber ended up being the heavy hitter of the Royal Air Force in the Second World War. As tensions with Nazi Germany rose in the late 1930's, Britain discovered it didn't have a bomber capable of delivering heavy bomb loads deep inside Germany. The original design submission by Avro took several years and multiple design changes to reach its full potential. The Osprey Air Vanguard Series book "Avro Lancaster" has the story, courtesy of author Richard Marks and illustrator Adam Tooby.What began as the two engine Manchester bomber would by 1942 become the four engine Lancaster, mass-produced to fill the need to carry the air war deep into the industrial heartland of Germany. As the author discusses, the Lancaster also proved suitable, when modified, for a variety of specialty missions, most famously the 1943 raid on the Ruhr Dams, dramatized in the movie "The Dam Busters". The book covers the development of the Lancaster in some detail, including the start and stop fielding of various modifications. Its operational history is summarized in the last third of the book, along with its postwar lives with various air forces and with several airlines. The text is nicely supplemented with a fascinating collection of period photographs, maps, diagrams, and modern illustrations. Highly recommended as a very readable introduction to a famous World War II war bird.