When reviewing your course materials list, confirm what each class is asking you to purchase. Some classes are very straightforward and list only one or a few required books. Others may have the same material but offered in multiple different forms (loose-leaf vs bound vs additional access code). All will be listed as required but you only actually need to purchase one of them. For example, some chemistry labs will list both the regular goggles and over-eyewear goggles as required, but you only need to purchase one set depending on whether or not you would wear glasses during lab.
Some classes have a mix of both required and optional course materials. Optional can be interpreted in different ways: some instructors will list material as optional as they are recommended pieces that will be helpful during your course, while some will list numerous items as optional and you only need to purchase one or two of them. Some textbooks are truly optional and the instructors list them to have them available to you. If you have specific questions about the books being used for your course (and why they are being used), we recommend reaching out to your instructor for clarification.