This is probably the best book on Spectral Analysis. A undergrad
level probability / statistics is all that is required for reading
through the book. The book develops the fundamentals of Spectral
Analysis clearly and thoroughly and takes the reader through the
various methods of spectral estimation. Parametric and
Non-parametric methods are discussed and there are a variety of
simulations that the reader can do in Matlab. The Matlab code is
also provided in the website for the book. After going through the
book, the reader would have enough knowledge in the field of
spectral analysis to make her prepared for advanced reading /
research in the subject. Also note that the book does not require
any in-depth knowledge of Digital Signal Processing so it can be
read by people in other areas who might need a knowledge of
spectral analysis.