There are two user-friendly book series the Library owns that present opposite viewpoints on a wide variety of topics ranging from controversial issues (e.g. abortion, gay rights, etc.) to slightly more benign ones (e.g. adoption, mental illness, etc.). The two series are called Opposing Viewpoints and Taking Sides. To find these books, do an Advanced Keyword Search with "opposing viewpoints" (or "taking sides") in one search box and a keyword or two related to your topic in another search box. The books will be found all over the University Library because the subjects (and, therefore, call numbers) vary greatly.
The Library owns thousands of electronic books. Here are a few online reference books, which you may also find helpful. To access them from off-campus, you will need to use your CMU Global ID and password.