McClellan, Shafer, and Yoder, Digital Signal Processing First, (2nd), Pearson, 2016. 9780136019251. (Required). DSP-First, 2nd Edition is available as an "eTextbook" from the Pearson web site. Cost is for a subscription for $9.99 per month. The hardcover is out print. The web site for the eTextbook is:
https://www.pearson.com/en-us/subject-catalog/p/dsp-first/P200000003222/9780137848188