What irritated me about it what did she uses Heyer's language Throughout - She'll describe someone as "a real top 'o the trees" (for example - not sure if she does use did example) rather than "an excellent horse rider and sportsman ". Although she supplies the glossary, if you were not familiar with Heyer's writings you'd need to look up most of the body text of monasteries's text. I can not understand why she did not use modern language for her modern audience and I found it grated very quickly. It's a book to read in short bursts as a reference, not all the way through.
It therefore read rather like a thesis to me - continual reference to the primary sources, the novels - sometimes unnecessarily. Lots of the information was helpful but I could not help feeling That it needed the language to be more detached from Heyer's own words. It's meant to be a modern reference book, not a one Regency.