Apparently the background for this book is the author's actual life - Renaissance scholar turned private investigator for a security firm run by a former CIA spook - although I'm pretty sure the plot is fiction. I'm thinking she can't talk much about her real life, so she fictionalized it instead.
It's a fun read, nothing too taxing - about a mysterious manuscript discovered in the process of renovating an Elizabethan-era building, which may or may not be Sir Francis Walsingham's long-missing collection of encrypted reports from his network of spies for Queen Elizabeth I. The story switches between the present day, when said scholar/private eye is hired to authenticate the book, and Elizabethan England, following playwright Christopher Marlowe as he acts as part of Walsingham's spy network (and ultimately meets his untimely end.) NOT A SPOILER! It's a fact that Marlowe died young, from getting a dagger in the eye. Silbert just puts that fact in the context of his role as a spy and provides an explanation for his death.