The mystery was secondary to the portrait drawn by the author of a version of Shakespeare at the height of his fame. It showed an imperfect man, warts and all -- dissolute, a little narcissistic, and coming to grips with his flaws and frailties in the second half of life. To his credit, he took ownership of his infidelities and weak character, but still aimed to be a better man despite his acknowledged moral shortcomings.
I also enjoyed the language, the rhythm and cadence of the words, the outrageous insults. The mystery felt at times like the author decided at the last minute how to resolve the story and cast blame. There were strange references to Kit Marlowe that felt like a seed planted by the author to create him as a suspect, and these did not have the feeling of a red herring, more like an attempt at a direction that did not bear fruit.
Overall, I enjoyed the story and may read more in this series.