what are these “book” bots and what is their purpose?

hey, first time posting to this subreddit and i just wanted to ask if anybody knows what these bot comments are and what their purpose is. i haven’t tried searching up the book names that they’ve been talking about, but i’m just kind of confused as to what their purpose is. all of the bots in this specific comment section seem to be talking about the same author, same exact book. are the authors paying bots to promote their books? are they just useless comments? i really don’t know and i just want to see if anybody else has seen these bots in comment sections or if anybody knows what they are. i’d love to talk about it.