This is the third book in the Sharing Knife series. I don't think it would be easy to understand without reading the earlier books, due to both the nature of the world and the backstory of the continuing characters. The first two books are outstanding anyway, so I definitely recommend reading the series in order.
This is a fascinating story of exploring magic in the Sharing Knife world. It's also a human story of individuals dealing with tough situations and learning how to deal with it, and on a larger scale a story that teaches some lessons on how to deal with ingrained cultural prejudices that ends with a pretty good conclusion about how individuals should deal with such things. It's not quite perfect -- it's not as absolutely fascinating as Beguilement, when the magic of this universe was brand new, but it's definitely a 9 out of 10.
**** PLOT SUMMARY -- MASSIVE SPOILERS ****
When we left our heroes, they'd just walked out of Dag's Lakewalker camp on a mission to try to make the farmers less fearful of Lakewalkers and more ready and able to cooperate against the malice menace. They return to Fawn's home and stay a while, but clearly don't fit in, so they plan to head down the river. Fawn's brother Whit is an obnoxious jerk of a little brother, but he really wants to come along, and manages to get himself included in the expedition. They come to the river at Pearl Riffle, planning to secure passage on a flatboat. Dag goes to the Lakewalker camp to ask for a knife in case he encounters a malice in his travels, only to walk to a crisis in Lakewalker-farmer relations. A couple of young patrollers got into a fight with the locals, and Remo got the knife he'd just been entrusted with broken. Dag and Fawn find a boat. Whit manages to get himself included in the crew. And then Remo runs away from his camp and joins as well. Berry, the boss of the riverboat, is trying to find her father and her betrothed, who went down the river last year and never came back. They head down the river, and then Barr, Remo's partner in trouble, overtakes them in a canoe, intent on dragging Remo back. Remo won't go. Then Barr really steps in it when he tries to use his ground to persuade Berry to throw Remo off. Because Barr's accused of having done the same thing to convince a farmer girl to have sex with him, this nearly gets him lynched, but when he's thrown off the flatboat, Dag expects him back, and when he shows up, Dag gives him a patroller-to-patroller talking to. Barr returns chastened and delivers a very strong apology, and Berry allows him to join the crew.
Interwoven with this, Dag has been learning more about ground work. On the one hand, he'd done a healing on Hod back at Pearl Riffle (since he felt responsible when his horse did a lot more damage than he expected in defending his pack), and accidentally beguiled the kid. With a couple more examples along the way, he figured out why that happened, how to reverse it, and how to prevent it in the future. On the other hand, he discovered and started to develop the ability to ground rip, in a very limited version of what a malice does. He was able to do it with oats, but he tried it with an annoying mosquito and his arm swelled up and he was ill for a couple of days.
About this time, the boat comes up to a tricky patch, and a small boat comes out offering to pilot them. The moment becomes very tense when they discover that one of the people is Alder, Berry's betrothed, but he's not elated to see her, and in fact he's very evasive. They work the story out of him, learning that a gang of river pirates took out Berry's father's boat, and Alder was survived but forced to join the gang. He could have snuck off, but he hung around because he wanted a chance to sneak off with some of the loot, so Dag figures he's culpable. With the knowledge of what's ahead, they stop the next few riverboats to put together a posse, which takes out the bandit cave with relatively light casualties, but the leader -- a renegade patroller named Crane -- and his two most vicious lieutenants. Dag stays and heals the two seriously wounded, including one of the leaders who has a fractured skull. While he's doing that, Crane and his henchmen have returned and grabbed Fawn. When Dag is confronted with Crane holding a knife to Fawn's neck, he reaches out and ground-rips Crane's upper spinal cord, paralyzing him from the neck down.
In the loot they find an unprimed sharing knife. Crane then is given the choice of hanging with the farmer bandits or of sharing, and sort of consents to the latter. Dag is not a knife maker but manages to make up the magic as he goes along, successfully primes the knife and then sticks it into Crane's heart.
All of the crew of the boat, now bonded together, are having trouble dealing with all this, but they continue down the river to the end and have a picnic at the sea. Whit proposes to Berry and she accepts, and they have a bunch of profound thoughts, and apparently decide that they'll stick together and help Dag with his mission to educate farmers about what Lakewalkers really are.