A tactilely pleasing book (it's sweat-proof!) with a highly functional design, Run Workouts for Runners and Triathletes is a great tool for trainers who coach runners as well as a gift for race- or triathlon-bound clients.
I really dig this book because it thoroughly describes the abbreviations for the training zone guidelines, gives very clear training plans based on the level of the athlete and describes each training run in such detail that even a novice runner could understand. But best of all, this book is well-designed. It's something you want to hold and to use. If you run or train someone who does, you need this book!