I have the song "Sons of Odin" by Manowar playing in my head whenever I think of this book, even though it's not particularly metal. However, I am a big fan of Matthew Davenport and I'm think this is his best book even though I absolutely loved THE TRIAL OF OBED MARSH and his ANDREW DORAN novels (particularly the short stories).
The premise is that Camelot is about to fall, as Camelot is prone to doing, but Merlin is spiriting away Excalibur in his hasty exit from the conquering hordes. A new wizard named Lord Bonnovist is devouring the power of other magicians while exterminating the rest so that he can be th sole remaining magic-user in the world. Merlin manages to escape but the price of his deal with the Lady of the Lake is a child that will eventually have descendants of her own.
Cut forward decades later and we now have Cremont and Dash Farthing that are living in the magic-hating kingdom of Camelot. The two troublemakers get into more trouble than they bargained for when it's discovered their grandmother is a witch capable of making the soil bloom during a famine. Well, this ends poorly for everyone and the two go to the Lady of the Lake to see if they're worthy of Excalibur as well as taking back the kingdom from the wizard and his puppet.
This is a pretty straightforward classic YA adventure story. You have the secret hidden bloodline, the Dark Lord, the children who are destined to overthrow the Dark Lord, and the struggles to get them into shape for doing it. That doesn't mean it's a bad story, though. Quite the opposite. This is actually a really good use of the classic adventure structure and doesn't overstay its welcome. Cremont and Dash are both likable young rogues as well as believable in getting themselves way in over their heads.
I thought it was a very fun story and think you will too if you check it out.