Books as scholarly sources are usually much longer than articles and offer in-depth research and analysis. They may also include more breadth on a topic than an article might. Books often provide comparative, interdisciplinary, or historical approaches to a topic.
"rolling stones" AND poland--> finds both Rolling Stones and Poland in the book or article records.
"rolling stones" AND (poland OR "eastern europe")--> finds Rolling Stones and Poland, Rolling Stones and Eastern Europe, or Rolling Stones and both Poland and Eastern Europe in the book or article records/descriptive content.