Yes, that is probably the case. Quoting from the post "Amazon is often the goto website for referring books, but many books have dedicated homepages as well as

Yes, that is probably the case. Quoting from the post "Amazon is often the goto website for referring books, but many books have dedicated homepages as well as pages pages on their publisher's website. Moreover, many freely available are referred frequently in comments, but are not considered in this ranking." The approach used here has limitations, I hoped to make that clear by pointing them out and choosing titles and headlines accordingly.