Yes, you should underline book titles in your paper. If you don't want to underline the book titles, another thing that you can do is italicize them. This is a way to let the reader know that you have borrowed an idea or quote from another source. This also keeps you from borrowing ideas and forgetting to crediting them to the correct source. Underlining book titles is a step that people often
. times forget. When you forget to do this, you can get in trouble for copying from a copyrighted source.