Books you get from the library and articles you find in the library databases are almost always reliable and credible. Those books and articles have gone through an editorial process; someone with expertise checked the author's facts and arguments before the book or article was published. You can read more about credibility and reliability here.
It's always a good idea to apply the CRAAP test to any source you want to use in your research. This test is especially important if you find a source on the internet rather than through the library.
When you find an article in the PUC databases or read a book or ebook from our collection, you can be fairly sure that they pass the CRAAP Test. Of course, you should check the publication date for Currency.
Websites are a different story. It can be difficult to know whether information found online is reliable or not. The following video explains how to evaluate websites.