Lilienthal's book is full of interesting comments such as this one from the introduction:
"With each advent of spring, when the air is alive with innumerable happy creatures; when the storks on their arrival at their old northern resorts fold up the imposing flying apparatus which has carried them thousands of miles, lay back their heads and announce their arrival by joyously rattling their beaks; when the swallows have made their entry and hurry through our streets and pass our windows in sailing flight; when the lark appears as a dot in the ether and manifests its joy of existence by its song; then a certain desire takes possession of man. He longs to soar upward and to glide, free as the bird, over smiling fields, leafy woods and mirror-like lakes, and so enjoy the varying landscape as fully as only a bird can do."
In addition to his romantic view of aeronautics, Otto Lilienthal was a careful observer of nature, an innovative scientist, practical engineer, and determined experimenter. His observations of bird twist and camber distributions, instrumented experiments to compute lift and drag, and flight tests of many glider configurations helped to transform aerodynamics into a serious field of inquiry at the end of the 19th century.