The book serves as a kind of living manual for the simulation software LTspice IV from Linear Technology. It explains all the functions, menus, and buttons of the software, and provides working examples and simulations that are demonstrated and explained. This book is aimed at all LTspice users: from beginners to professionals involved in the development of complex circuits. For over 20 years, LTspice IV has been the go-to simulation software. Unfortunately, the help file is the only documentation available for this software. It is incomplete and lags far behind the software's development state. Many commands and functions are not explained or are only inadequately covered. As a result, specialized forums on the internet often become the last resort for questions and problems related to the software. This book fills that gap! It offers a comprehensive explanation and description of functions.