There are spoilers related to the first two books of the trilogy in this post. Read at your own peril.
I feel like the author sort of lost the plot in this one, even accounting for the fact that it is difficult to end a Robin Hood story without just killing everyone. A.C. Gaughen justifiably wanted her characters to get their happy ending. Unfortunately, given the first two books, the idea of a happy ending was going to be very difficult to pull off.
So, in this book, we start with Scarlet in prison, held captive by King John. Little John is dead. The band of merry men are neither merry, nor or they actually a band. The players have been scattered to the four winds, and we don't meet up again with Robin until more than 50% of the book has been read.
I'm reminded of The Hunger Games, a bit, actually. I know that a lot of readers were really pissed off at the ending of The Hunger Games, but I liked it, and felt like it had a realism attached that made it believable. For me, this ending, where Robin and Scarlet get their happy ending, get their earldom, and "beat" King John, well, it just didn't work for me because I couldn't buy it. I couldn't suspend my disbelief.
I liked the idea of incorporating a female heroine into the Robin Hood mythology. But Scarlet was so reckless that frequently I was just pissed off at her. Her recklessness, which occasionally rose to the level of stupidity, ended up getting a lot of characters killed protecting her.
Robin Hood can be seen as a symbol of resistance against an unjust government, but the end of the Robin Hood story is open-ended. He can spark a revolution, but there is no mythic tale of his life or death - no great betrayal like the one that marks the death of Arthur of Britain. He appears in mythology, fully grown, and then disappears as well, once his purpose is served. While this open-endedness might look like it promotes freedom to end his story however the author chooses, in reality, I think that not having a well-understood mythological framework for the ending makes it difficult to write a believable but still non-heartbreaking ending to a Robin Hood retelling.
I'm not quite sure where I am going with this post. But the standard happy ending, which is what this book had, just didn't convince me. Boy gets girl, Girl gets castle, The end. I would've preferred a chancier end to this story.