Sovereign is the third of Sansom's Shardlake mysteries and they are all excellent. I reviewed the first here and for some reason haven't reviewed the Dark Fire the second installment.
Anyway, Sansom is a skilled writer, he creates a real sense of the time, the smells, the curses, the mood of the age in England under King Henry VIII. There is power, politics, religion, riches, law and of course a murder to solve.
Shardlake is a good detective, this hunchback lawyer trudging upto York and reluctantly being drawn into court politics and the affairs of state aided by the lively Jack Barak. The historical backdrop is plausible framed by real historical events and the mytery is both challenging enough, with a good enough twist yet you can also figure it out, if you're so inclined.
Anyway, if you want a cracking read and enjoyable thriller, I'd highly recommend this series.