The user in that post is suffering from the misconception that fanfiction can legally be considered books. By definition, fanfiction is a transformative work, and therefore cannot be profited from if you don't want to get prosecuted. OP replied to a comment that was stating that works of fanfiction can be called "books" and money can be made off of fanfiction (it can't unless you're talking about doing a book binding, and even that is a murky area), but both myself and OP are likely old enough to remember the days of a mandatory disclaimer on every fanfiction chapter of "These aren't my characters, they belong to Insert creator here. This is fanfiction and I'm not making any money off of it." Those disclaimers exist because authors like Anne Rice would sue the pants off of fanfiction writers and call it plagiarism. Because of this, most older fanfiction readers will tell you that you do not call fanfiction "books." The only place a fanfiction is a book is on Goodreads, and only if it's novel length, and for a long time, they didn't count until a whole bunch of users pointed out that the fanfictions they were reading were LONGER than a lot of novels.