The book "Johnny Nelson. How a former pupil of Hopalong Cassidy of the famous Bar-20 farm in the Pecos Valley did an act of chivalry, and what came of it" by Clarence Edward Mulford is an exciting adventure about a boy named Johnny Nelson. Living in the far west, he finds himself in the middle of a tense situation where he will have to prove his courage and skill. This book tells about the courage and magnanimity of a boy who entered the world of exciting cowboy adventures. Together with Johnny Nelson, the reader travels through the boundless prairies and cowboy settlements, where each meeting brings new challenges and incredible discoveries.