Nice -54, Blighty!
Tin brings up a good point, there's still room for advancement in these. Before Shreckling and a couple other pioneers, it was thought to be impossible. If I understand the story correctly, these guys crunched the numbers and on paper, it SHOULD work with a 1 stage centrifugal compressor... and sure enough, it did.
There was supposed to be a master craftsman from Britain who made a PERFECT miniature of an axial flow turbojet some years ago, and the model did not sustain... the air flow doesn't scale.
Anyway, the Schreckling book is good, as is Kamps, but as Tin says, there are better designs now.