Sounds like one of those too-good-to-be-true schemes.
If it's so great, why isn't *he* selling books, instead of cutting you in, (for a mere $5k), for a share of a somewhat limited market ?
Would you pay $500 for a book ? I certainly wouldn't.
And if you can't sell these magical tomes (assuming you actually *get* them in the first place) it's bye-bye $5k.
By the way, how do you know this scheme is "perfectly legal under the law" and that "everyone who joined the program have all managed to sell their books and gain profits" ?
Because this guy *told* you ?