Q. When looking for books there are required, recommended and suggested, what is the difference?
Required books are for core learning and will be used in class for assignments and lectures. Recommended books are not required for the course, but the readings are very important to clearly understanding a topic. Suggested readings are mostly for when you would like to know the full extent of a subject. They are not required for learning the course's topics, but they will improve your understanding of the material.
However, this is the general rule, and not set in stone. I would check with your professors to see what their opinion of the matter is.