I agree the ebooks from CBM are excellent and both vol1 and vol2 are well worth having. I also rate the books from Julian Voigt C2G - in particular there are many insights into technique which I personally have found extremely valuable (particularly in vol2). I spent a lot of time searching for this, that and another special ingredient but in reality it was my technique that was at fault - Julians books have helped greatly here.The price of these books is cheap and there are associated video links which I again have found invaluable.
I also agree with the previous comments the 1TBSP mix powder is a little excessive (at least for my taste) - but this will depend a little on the base gravy recipe you are using.
Regards
John