The time and place Mary Queen of Scots - A Queen without a Country covers is full of very hard things : Immorality, assassinations, wicked people and political turmoil. This is handled with a great deal of tact, which helps make the book suitable for a younger age than would usually be the case though some of the necessary references to violence and subtle hints of immorality may make it still unsuitable for younger children.
My only real quibble with this book is that the use of astrologers is not clearly shown to be negative. True, Queen Catherine's firm reliance on them is seen as superstitious and a bit silly, but their power is not completely written off and they are certainly not portrayed as sinful. This is a reoccurring topic in the story, but is not overplayed and could easily be skipped in a read-aloud.
Overall though, I found Mary Queen of Scots - A Queen without a Country to be an engaging, well written and believable story.