The book "Sturm-Liouville Theory and its Applications" offers a comprehensive introduction to Fourier analysis and special functions based on Sturm-Liouville theory in L2. It was developed from a course designed for advanced students and places particular emphasis on the convergence properties of sequences of numbers and functions. The text assumes a solid understanding of advanced analysis as well as knowledge of ordinary differential equations and linear algebra. The clear and rigorous mathematical presentation is both reader-friendly and well-motivated, supported by numerous examples and applications that illustrate the theory. Although the book is primarily aimed at mathematics students, it will also be of interest to students in related disciplines such as physics and engineering, as Fourier analysis and special functions are often used to solve linear differential equations.