I have the book and, like Curry2 Go and others I think it is good, but not VERY good in as much as the editing leaves many unanswered questions especially around measures etc and with that particular book you will find yourself jumping around from section to section alot. Much if not all of the info can be found on here.
My advice would be to pick one and stick to it for a few weeks . ie C2Go, undercover or .............. stick with Chewy, CA etc from here. I found that I was jumping around all over the place and this in itself caused more confusion as they all do things a little differently. I have made four different gravies now and to be honest I think they are all good and are all basically the same with just the odd tweak, omission or addition. They are what the name suggests, as base, and it is the proper cooking out of the onions that, for me anyway, is the key.