For books that are published in more traditional manners, digital or paper, there is normally a credible publisher, editors, sometimes a foreword from a known figure, reviews from critics or experts in the field, and often a bio about the author explaining who they are and why they wrote the book etc. These different elements are all signals of reliability, they help to convey that the content is more than just fluff around an attention-grabbing title, that it has depth and quality and holds up. The whole publishing business has put massive effort into establishing and building these markers of trust.