answer:In the US, that would likely not stand under our fair use law. Fair use law takes into account the amount and substantiality of the original work being copied when determining whether use is fair. Using a small version of a whole painting for a search engine thumbnail has been determined fair use. Copying a choice 400 words of a memoir was considered not fair, because it used “the heart of the book”. If someone could watch your YouTube videos instead of buying the audiobook, the publisher and author could rightly take exception to your use.