THIS is a good book. It is meant for actors AND writers, and I am both, and therefore well placed to gauge all it has to offer. This book will help you choose, and orchestrate (Egri vocab), and shape comedy characters, and help you to keep them true throughout a story (writing). In acting, so often scripts seem barren of detail, so it's hard to know who the hell the character is, but this book helps to impose a finite though liberating attribute list for each character type, and you'll therefore always be able to fashion appropriate character behaviour regardless of the situation or storyline confined within.
It won't write your stories for you, nor get you up on stage or in front of camera, but this book will help you arrive at funny, viable characters (writing), and give you the knowledge and confidence that you are performing your character truthfully (Stan'i vocab).
Many books are 'jack of all trades,' dissipating and spreading themselves thin, but this book capitalises upon the close relation and synergy between acting and writing. (It is no accident that formal theatre arts courses include writing classes.) That said it is more than worth the price if you are at present only into one of said disciplines...