Hi Megan,
Not exactly screen reader specific, but Using This Book – Accessibility Handbook for Teaching and Learning has instructions for navigating Pressbooks using keyboard navigation and screen readers. Specifically focusing on moving between pages and using the table of contents menu would be the priorities for screen reader users.
Pressbooks is an accessible platform. Of course, it’s easy to add inaccessible content to it. As far as optimal screen reader, it shouldn’t matter. I have tested Pressbooks with JAWS, NVDA, and VoiceOver.
Luke