Using "what" alone is usually asking for a more specific answer. For example: What classes are you taking? Answer: I'm taking Calculus, Physics, Astronomy, and a few others. Using "what kind of" is asking about a general type. For example: What kind of classes are you taking? Answer: I'm taking mostly math and science classes. So for your example, if you want to know the types of books he reads, you would say "What kind of books does he read?" Sometimes, however, the phrases can be used interchangeably.

In the examples: "What books does he read?" and "What kind of books does he read?" They both mean the same thing, but by using the phrase "what kind of", that is a more specific way of asking the question.

"What books does he read?" --- прямой перевод с русского нейтивы так не говорят