Author quickly explains short board fundamentals - water start (in detail), clew water start, etc.
Then he shows common freestyle tricks - helicopter, sail 360 and others with lots of photos but little text (5-7 pictures for a move with short titles). These explanations are like that can be easily found in the Internet.
Other subjects - jumps, loops, wave riding described in the same manner. This book is pretty out of date now, so modern tricks are not explained (spock, volcano ...).
It is of course not a beginner book but probably it can be useful for more advanced sailors.
My opinion that it is better to buy 2-3 windsurfing videos than this book.