I use the Arduino platform for prototype projects or projects that I don't want to spend the time to build a new PCB with a microcontroller. I have used the first edition of Exploring Arduino for years when I came across the second edition on Amazon. The second edition has added many new chapters and structured them into an easy to reference format based on applications. This makes Exploring Arduino easy for beginners to get started as well as providing a quick reference for more experienced users. I recommend this book to anyone using the Arduino. You will want to have a copy close at hand.