If I were Amazon, I would curate reading lists for different topics and make the whole set available as a single product.
Perhaps pair up with The Great Courses or one of the universities like Stanford or MIT who are embracing online learning to generate them. Maybe get a nobel laureate or other luminary to sign off on the list in a subject they're familiar with.
I need to shore up my knowledge of statistics. I can go out there and read reviews and use the Amazon ratings systems and so on to find the best stats books, but that takes time and is hit-and-miss. That distributed, peer-driven recommendation system works great for novels and niche non-fiction, but for large topics like Data Structures there are some more-or-less canonical books. I want someone to quickly point those out to me so I can get started.
I want to be able to go to Amazon.com and have them give me the three or four best books on Linear Algebra so I can dive in without having to poke around in reviews and ratings and so on.