The book is very good. The author clears up a lot of the confusion of late model BF-109G's. Plus review the BF109K's also in the book. If your a modeler one can now build a BF109's based on what factory reworked the aircraft. Addition information on all the different Tall tail rudder and there variants. This surprise on now any different styles of rudder. A must of a serious BF109 modeler of historian.