This alternative Britain, where everyone owes a decade of slavery to the magic-using elite, is grimly plausible. Take away the elite's use of magic and you're close to how Jacob Rees-Mogg and his ilk believe England should be.
The main characters are all under twenty. Their inexperience helps with the world-building but it also gives a YA tone that dampens the rage I should be feeling at these magical Tory Tyrants.