We get this from two viewpoints. Mal Catlyn is a rogue and swordsman, a scion of French nobility (much good it does him in Protestant England; he's dead broke). Coby Hendricks is a costumes manager in a theater, staying out of the limelight because she's secretly a girl. Okay, Mal's sidekick Ned also gets some page time. (Ned has a crush on Mal. Coby winds up with a crush on Mal. Surprisingly, this is not a romance-triangle plot.)
My problem with this book is that it takes damn near forever to get going. There's vast swathes of minor politicking around the theater, the skraylings, the collision between the theater and the skraylings, the murders in the theater, the attacks on the Skraylings, the spies... Naturally Walsingham is involved. (Kit Marlowe is only namechecked; he's dead.) But none of this seems to be going anywhere, until more than halfway through the book. Then Mal's persistent nightmares about skraylings turn out to be all sorts of relevant and a nasty, nasty scheme makes itself known.
Things kick into high gear for the final third of the plot -- kidnappings, fires, divers alarums as they say -- but I'm afraid that my interest never quite caught up. Plus of course only the most immediate threads are wrapped up, because sequels. That didn't help. The characters are engaging, but I wanted a reason to care where they wound up.
On the plus side, the author has researched the heck out of the Elizabethan era. It shows -- not in a "let me show you my research" way, but in ubiquitous fine detail. Character cut their pens, buy clothes, play tennis, and go drinking in period-appropriate ways. It's the sort of thing you don't notice is missing in other books, until you see it done right in this one.