Math Is Fun Forum

Cool, I've never seen anything like this. Haven't even heard of this. Although I have already stopped buying books, I read everything online or in a folded version. Recently read "childhoods end", I used https://freebooksummary.com/category/childhoods-end for this. After this, I myself wanted to have something like this. I just don't get it, is this a special book or a coincidence?! Waiting for an answer..