This incisive text, directed to advanced undergraduate and graduate students in mathematics, physics and engineering, deftly combines both theory and practical example to introduce and explore Fourier series and orthogonal functions and applications of the Fourier method to the solution of boundary-value problems. 570 exercises.
Here's a sample of other books in this Dover category
An Introduction to Lebesgue Integration and Fourier Series by Howard J. Wilcox, David L. Myers Undergraduate-level introduction to Riemann integral, measurable sets, measurable functions, Lebesgue integral, other topics. Numerous examples and exercises.
An Introduction to Fourier Series and Integrals by Robert T. Seeley This compact guide emphasizes the relationship between physics and mathematics, introducing Fourier series in the way that Fourier himself used them: as solutions of the heat equation in a disk. 1966 edition.
Fourier Series and Orthogonal Polynomials by Dunham Jackson This text for undergraduate and graduate students illustrates the fundamental simplicity of the properties of orthogonal functions and their developments in related series. Includes Pearson frequency functions, Jacobi, Hermite, and Laguerre polynomials, more.1941 edition.