This comprehensive book on Applied Operator Theory was designed by the author to fill what he perceived as a gap in the literature of mathematics, which often treated the subject in a manner he described as both sketchy and incomplete. In writing A Beginner's Guide to Applied Operator Theory, the author had the goal in mind of writing the finest book that has ever been written on the subject. Generations of teachers and students have benefited from Hurwitz's thorough presentations and concise results. Suitable for advanced undergraduates and graduate students of mathematics, his treatment examines a wide range of topics giving the reader a breadth of understanding and insight into current mathematical research areas.