I think I discovered The Tudor Secret on Goodreads. It’s C. W. Gortner‘s third historical novel and the first in his Spymaster Chronicles series featuring Brendan Prescott’s interactions with the Tudors, primarily Elizabeth I.
The novel is set in 1553 in the days immediately before and after the death of Edward VI.
I enjoyed it a great deal and was happy to learn on Gortner’s blog that the sequel, The Tudor Conspiracy, is available. A reading guide is available on the Macmillan website. You need to scroll down almost to the bottom to find it.