I have mixed feelings on this one.
First off, I've never read any of the Robin Hood legends, and the only movies I've seen are Prince of Thieves and Men in Tights, so I can't in anyway compare this to the source material aside from the obvious - Marion is Robin's sister, and Rob's gay. I remember John and Will from the PoT movie, but I pretty much don't know who anyone else is. So I'm just going to review this like any other book.
As a fantasy adventure historical, this is great. Very imaginative and takes place in roughly the same time frame as the original RH stories. The pagans are still very much a presence but slowly being squeezed out and pushed to the sidelines by the Christians. There's a lot of world-building here but none of it feels overwhelming. The social and religious strife between the two sides in this conflict is realistic and rooted in our actual history, while adding in elements of fantasy. It's a good meld of the two.
As a romance, you could pretty much pull it out of this book, and plop into any other YA/teen in-the-closet/coming-out story and it would be exactly the same as all of those, along with way too much sex. Except, you know, actual lives are in danger and not just teen angst making it feel like that's the case. Rob's especially pig-headed, and I wanted to smack him a few times, especially at the end, but the book does that well enough when he decides listening to his dick is more important than being stealthy, so I'll refrain. ;) Gamelyn's struggles to accept himself despite his upbringing were interesting though, and I liked that we get to see both accepting and fire-and-brimstone views on sodomy by the two prominent religious figures.
The narrator does an excellent job bringing the story to life and voicing all the characters. He's easy to understand and is able to do a full range of vocalizations for both the male and female characters, and he's pretty great with the accents too.