College classes sometimes require much more textbook reading than students are used to. Just simply passing your eyes over the words and skimming the work is not an effective way to learn the material.
How to Use Your Textbook offers suggestions for ways to utilize books (other than a door stop).
This Reading Strategies video shows you how different kinds of texts require different types of approaches to reading.
The SQ3R Reading Method explains one particularly effect approach to active reading.