Catlady, schools do have summer reading lists, and library periods and study halls, but the time in class is supposed to be spend doing something a bit more guided and structured. Anyway, if everyone got to do what they wanted, it would be called schoolplay instead of schoolwork.
In any case, in MY high school. we were almost always expected to 'just read the book' first, then discuss it, especially with shorter works, then discuss it...or more often, write a book report.
For every kid who would have been happier being left to read the book, there is at least one who would not bother to look at, and would do the book report based on the back flap material*. Some people need to be guided through a chapter at a time.
Perhaps, the approach they take is the worst possible approach, except for all the others....
*ok, that was usually, me.