"Green Rider" has some decent fight sequences and an occasional moment of cleverness, but honestly, if you're an adult looking for the next big thing in high fantasy, this isn't it. Kristen Britain's characters are lousy, her plotting is hodgepodge, and her writing is never better than Mercedes Lackey's worst books. Overall, this comes across as overhyped, underwritten junk for teenagers, a waste of time for any reader who's made it past the "Sweet Valley High" stage.
The main character is Karigan, a young girl who encounters a dying messenger from a guild called "The Green Riders". Forced to take over the man's mission, she soon gets caught up in a series of wild adventures and chased by eight-legged beasties and an assortment of not very frightening villains such as "The Grey One". (I think that name was only chosen because "The Dark One" was already taken.) Characterization is appallingly thin, with no attempt to move the central character beyond the stereotypical 'spoiled girl encountering the real world for the first time'. The author doesn't seem to understand that a story like this won't succeed unless the main character is likeable and sympathetic; her protagonist comes across more as irritating. Minor characters suffer even worse development, and they tend to blend together since they don't serve any purpose other than to gives Karigan advice or assistance for a few pages and then disappear.
Of course, a simple quest or adventure story can be enjoyable even if it doesn't aspire to be great literature. But for this to happen, something must occur to build up tension and suspense, or else the story just flatlines. You can never really feel that Karigan is in any danger in "Green Rider" because some new character or concept always get introduced to the story just in time to save her. And there's one scene where she manages to escape from two bad guys just because they start fighting with each other. But wait, why did they start fighting with each other? It's never explained.
One of the first things your high school English teacher probably taught you is the 'show, don't tell' rule. Kristen Britain must have been absent that day. When she wants to say that Karigan is angry, she just writes "Karigan felt angry", or has her say "I am angry", but she doesn't make the character's words or actions sound angry. This is a critical difference, and it is symptomatic of Britain's immature writing style. Also, she chooses too many of those unpronouncable fantasy names with too many apostrophes. So in summary, let me just say that I did not like this book. Will children like it? I doubt it.