This kicks off a second round in the universe of the Obsidian trilogy (The Outstretched Shadow, To Light a Candle, and When Darkness Falls). It's a thousand years later, so the characters from the first one (even a few who are still alive) are legendary heroes. I don't think it's necessary to read the earlier books to understand this one, although it does let you understand a few jokes.
This is a more pointedly young adult story than the earlier ones. The main characters are nominally 17, but seem to think and act like they're 12, to an extent that diminishes the story. It's also a quicker and easier read. The problems of ordinary people being forced into the roles of heroes is a major theme. It's easy to read and fairly enjoyable, but not terribly original. 7 out of 10.
**** PLOT SUMMARY -- MASSIVE SPOILERS ****
Harrier and Tiercel are boys coming of age in a latter-day Armethalieh, an Armethalieh which has no magic. There are Wildmages in the world, but they are very seldom seen, and the High Magick is quite forgotten. The Endarkened have been gone from the world for a thousand years of living happily ever after. But trouble is starting. Harrier, the more physical of the two, gets a book from his world-traveler uncle which he gives to the more bookish and pathologically curious Tiercel. Tiercel reads the book and pursues this weird idea that there is another kind of magic, which he gets the idea anyone can do with training. When a ship limps into the harbor claiming to have been attacked by a kraken, he tries to do a spell of Knowing to find out if it was true -- and sets his bedroom on fire. He also starts having terrible nightmares about a lake of fire and a beautiful woman who's trying to tell someone something. He has such a strong sense of evil that he becomes quite ill from not sleeping. Then he learns a little more about the High Magick -- that only a few people have the magegift, and that when it manifests, if it is neither suppressed nor trained, the mage dies. He becomes convinced that he needs to go find a Wildmage, and he and Harrier head off to Sentarshadeen. On the way they meet a young centauress, Simera, who saves them from bandits on what's supposed to be a safe bit of road. In Sentarshadeen they meet a priest who is really a Wildmage but won't admit it, who sends them on to Ysterialpoerin. (The old elven cities are strictly human now.) They meet another Wildmage on the road who gives them some gifts. Then they find a town missing all its people, and Simera is killed by goblins. In Ysterialpoerin, they visit the caves, and sneak down to an off-limits area where they meet Ancaldar who leads them through a portal to the elven city. Tiercel finds the library he wanted, but learns that by himself he lacks the power to do anything useful with magic. He needs a dragon, but when he learns that if he bonded with a dragon, the immortal dragon would die when he did, he is horrified.
While the above was happening, we also meet Bisochim, a wildmage of the fierce desert nomads. He's off being a hermit, and encounters a dragon who got caught in a storm, whose wings were injured. They try to avoid it, but they bond. And Bisochim starts having visions sent to him about how there is a way that he can extend his lifespan and save Saravasse his dragon from his mortal doom. The visions spur him to try to kill Tiercel from afar, but Tiercel uses fire (the one spell he really knows) to counter the sending of ice. Then Bisochim conjures a being out of the fire that he sends to take Tiercel out, only the being has a will of its own and just wants to test Tiercel. And Tiercel seems to pass the tests, at least partially.
As we near the end of the book, Jermayan (who is extremely ancient even for an elf) is at death's door, but somehow Sandalon, the king, who is very old himself, has come up with the idea of casting a Great Spell to transfer Ancaldar's bond from Jermayan to Tiercel. The Great Spell utterly consumes the mage and dragon that cast it. Ancaldar does not want to do it; he'd rather die than live without his Bonded. Tiercel is horrified that the the king and his dragon would kill themselves for him. But Jermayan insists, and they go through with it. Predictably, once Bonded, the two start to appreciate each other more. Harrier, however, seems really upset that Tiercel suddenly has a new best friend and all he can do is drive the wagon. Then a unicorn shows up and delivers the Three Books to Harrier; he is to become a Knight-Mage, the protector that the pathologically trusting Tiercel needs.