The book by Jure Leskovec, Anand Rajaraman, and Jeff Ullman is based on Stanford Computer Science course CS246: Mining Massive Datasets (and CS345A: Data Mining). The book, like the course, is designed at the undergraduate computer science level with no formal prerequisites. To support deeper explorations, most of the chapters are supplemented with further reading references. By agreement with the publisher, you can download the book for free.