If you are interested in exploring specific parts of Klein's work further, I can help you:
Felix Klein’s "Development of Mathematics in the 19th Century" is a seminal two-volume work bridging 18th-century classical methods with modern, abstract mathematical foundations. Based on lectures from 1914–1919, the text outlines the transition from individualistic research to institutionalized, rigorous, and unified mathematical systems. The work is available in digital archives, such as the Internet Archive. development of mathematics in the 19th century klein pdf
The study of properties (like length, angle, and area) that remain invariant under the group of rigid motions (translations, rotations, and reflections). If you are interested in exploring specific parts