A friendly and easy introduction to the subject. As a cosmologist, I know well what Fourier transforms are but damned if I ever had to actually compute a DFT in an applied setting, worrying about windowing, aliasing, and Nyquist frequencies. Lyons takes you by the hand and whispers, calmly but assuredly, "it will be all right, child." Overall, a gentle and useful guide to the concepts underlying DSP.