I used this book as an undergrad many years ago in honors first-year physics (along with Purcell's excellent E&M book from the Berkeley Physics Series), and have referred to it from time to time since. It's a clear, patient, matter-of-fact introduction to the subject which takes the time to clarify many of the obscure and seemingly contradictory aspects of special relativity. It's written about at the level of the famous Halliday and Resnick university physics books. I found the book to be very useful as an introduction. If you already know the subject, and need an advanced reference, this will be too basic, but as the title says, it's an "Introduction".