The book is a local historian's labour of love: thorough in its research on documents (including several poems in Welsh about Blanche Parry's immediate ancestors) and also on artworks which may depict her and places with which she was associated. It does not have a lot of scholarly apparatus; there's little here about the nature of kingship or queenship, and I found the discussion of religion a bit confusing - Richardson suggests that Blanche Parry must have played an important part in getting the Bible translated into Welsh, but there is no smoking gun.
The Welsh link does intrigue me as an area where I would like to understand better what was going on. Apart from Blanche's family, and her cousins the Cecils, another Welsh family had made it big in politics a bit earlier - their home county of Hereford had seen the beheading in 1461 of Welsh knight Owain ap Tewdwr, whose grandson Henry Tudor took power in England in 1485 and was Elizabeth I's grandfather.
However, I was entirely satisfied about the one thing I really wanted to know - did Blanche Parry have any dealings with Sir Nicholas White in Ireland? As it turns out, it's absolutely clear from his surviving correspondence that she was his channel to the queen. His main contact in London was Cecil / Burghley, who he had known since they were both young men; presumably he had encountered Cecil's slightly older cousin as well. When he successfully raided the Earl of Desmond's treasure train, he sent the spoils to Cecil with instructions to split them with Blanche. (See previous entry.) So I got what I wanted from the book, even if it's not the most academically rigorous volume I have read on the period.