To be honest, I am not sure that there is a way for you to go about this without getting sued. By giving away the plot and conclusion (or hooks) of copyrighted books and ultimately making money from you, you will devalue, in some capacity, the intellectual property of the copyright holder. Moreover, this could be viewed as a willful infringement, which is actually where the big money law suits take place.
Generally speaking in an infringement scenario, the best defense is that you did not knowingly infringe upon the copyright of another. While this is not as blatant as republication, it would be difficult to defend against willful infringement claims by giving away the story - particularly for money. Willful infringement must be proven by the IP owner to receive punitive damages and attorney fees.
To be quite honest with you, though the idea in a vacuum is pretty cool, the only way you could get away with this would be to have a license to do so from the IP owners. Otherwise, quit honestly, you are setting yourself up for liability for infringement that could be very costly...particularly on books of note - like best sellers that generate millions in revenue for their owners.
In short, I caution you against this pursuit without first obtaining a license from the owners of the IP.
Please rate my answer positively and let me know if you have any additional questions or comments.