If you don't get something good the first time you buy a book, you might with the next book, or you might not. Either way, the house wins.
It should be regulated as gambling, because it is. There's no metaphor — the only difference from a slot machine is that books will never output cash directly, only the possibility of an insight or idea that could make money. So if you're lucky with your first gamble, you'll want to try another.
Gambling all the way down.