The required textbook for the course is OpenStax: Precalculus, by Jay Abramson, et al. This book is freely available online. A list of the topics scheduled to be covered can be found on the course calendar.
You can buy a physical copy of the textbook in the UC San Diego Bookstore or you can get a physical copy from Amazon for a reasonable price. However, the book was designed to be a free electronic book, and it can be accessed that way directly from OpenStax. Please be aware that you will also need access to the Edfinity online homework system, which you will access through Canvas. You can buy access directly from Edfinity (for one quarter) for $29.