This book is set in a real time and place, namely the days leading up to Edward VI's coronation and the boy kink is one of the main characters in the work. The book concerns the accidental swapping of identities between Edward and Tom Canty a beggar of the same age and appearance. The book has aspects of a historical novel, aspects of a fairy tale and is a social satire of the human condition in general and class differences in particular. It is part of the joke that there is essentially nothing to distinguish between Tom and Edward except the accidents of their birth.
The book is funny and light and Twain manages to balance the disparate elements together fairly well, which have a tendency to pull in different directions. Twain does a competent job of writing Elizabethan dialogue that is both accessible and funny.
The book is good and worth reading, but not in the end great. Entertaining and without surprises. It is pretty much what you would expect.