"A Practical Guide to Ubuntu Linux (Fourth Edition, 2015)" by Mark G. Sobell is a comprehensive textbook focused on the subject area of operating systems, specifically Linux. Published by Prentice Hall PTR, this trade paperback book covers the essential aspects of Ubuntu Linux in a practical and easy-to-understand manner. With 1320 pages, this updated edition is a valuable resource for anyone looking to deepen their understanding and proficiency in using Ubuntu Linux for various computer-related tasks."