This open-access book offers an introduction to Felix Klein's concepts while highlighting advancements in college instruction and K–12 mathematics that are connected to Klein's principles and date from the previous century.

It explores the significance, legacy, and implications of Klein's views in a contemporary and foreseeable global setting.

The book gives suggestions and advice for addressing current issues in secondary school mathematics instruction and teacher preparation, demonstrating how many of Klein's concepts might be reinterpreted in light of the current situation. It demonstrates that while traditional ideas are eternal, they require competent, dedicated, and aggressive people to make them a reality.

Felix Klein emphasized the value of pondering mathematics teaching and learning from both a mathematical and a psychological or educational point of view throughout his professional career. In addition, he developed concepts in university lectures for student teachers and vigorously advocated for the modernization of mathematics in the classroom. He later combined these ideas in three books on elementary mathematics from a higher perspective, which were published at the turn of the last century.