This is an interesting work, where clearly a lot of effort has gone into it. However, I was somewhat disappointed by the fact that the author has used, for his main source, Casaubon's printed version of Dee's works, which contain many errors. One example will suffice: the word 'Peral', to be found in Key 5 (according to Leitch and many other authors), never appears in Dee's works at all. It is in fact a misprint for 'Peoal'. At least Leitch has inserted it in its correct position. There are a number of other spelling errors throughout the Keys. I would also strongly argue against some of the numbered listings of the Keys near the beginning of the book, where, in my view, they are clearly wrong, but it was nice to see that in the first Key he lists 86 words (despite the fact that many individual words are numbered incorrectly), which is certainly correct. My last criticism is with accents: Dee never uses the circumflex (found throughout this work, and interpreted as as long vowel); all these should be replaced with a breve (from the Latin brevis - short), being a short vowel or syllable. The number of errors in this work are just too numerous to list, simply because the author is not using original source works.
To be of any real value, works such as this must be based upon Dee's original manuscripts; relying on printed sources is a serious mistake. I have found no printed source which is free from errors, some of them are appalling. My own 40 year study in this field may one day be published. As a final note, I would say that, a revised and corrected version of this work would be a valuable addition to Enochian (not a word Dee ever used) literature.