"How? or, How to make free time useful for boys and girls" is an educational book written by the famous authors Holbrook and Kennedy. In the book, children will find a large number of exciting tasks and interesting experiments that will help them spend time usefully and fun. The authors offer a variety of games, local history excursions and even simple scientific studies that will develop children's imagination, logical thinking and creativity. The book will be an excellent guide to the world of interesting activities for little inventors and researchers."