If he choses the right type of books, I may agree to the deal too ;-)
Me and my friends often judge people by the books they read and when a relationship breaks up we are like "I always knew he was not the right guy, because he read this and that book"
I do believe that Charles wanted to support Diana in her royal duties, but maybe she misinterpreted the gift of books. Maybe it would have been better if they had taken some time to browse through a library together and talk about the books instead of putting a huge stack of books on her desk.
(Again, we do not know in which way the books were presented to Diana, so we can only speculate!)
When I try to learn something completely new, I prefer to talk to someone who takes the time to explain things in detail and answers my questions, later when I have also found enthusiasm for the topic I start to look out for books myself...
Some people are more into books and need them as much as they need water and food, but for other people reading is something they only do when they have to do so (e.g for school or work). Iit is difficult to convert non-readers to bookworms, unless they find an author or genre that really fascinates them, they leave most books untouched