The Original, now updated and comprehensive latest edition of the Model Rocketry bible
G Harry Stine along with the Estes family were responsible for getting model rocketry started in the late 50s. This seminal book, now in its 7th edition, tells you everything you need to know about building, flying and designing model rockets. Old Harry Stine has blasted off for the last time but his son Bill, the founder and president of Quest Aerospace, has edited the book to bring more modern materials and motors into its coverage.
It might be a little hard going for the very young, the technically challenged or very inexperienced rocketeers but it is the book you will refer to again and again even after you have flown High Power Rockets at Level 2. Particularly since there is a new chapter on high power rocketry and electronic payloads and computer rocket design.
Keeping up new rocket technology is hard and any printed book will lag behind the web but fundamental physics and applied aerodynamics haven't changed much in the last 50 years, let alone 10. The book will be and excellent reference for years to come.
This is the official handbook of the National Rocketry Association (US) for good reason. If you are keen, the Stine book is where you can find everything you need to know.