What is a theme of Touching Spirit Bear and textual evidence that explains the theme?

Touching Spirit Bear by Ben Mikaelsen is a coming-of-age story about a young man named Cole who undergoes a healing treatment on a deserted island as punishment for violently attacking another boy. Cole is taken under the wings of two men: 
Garvey—Cole’s parole officer who got him into the rehabilitation program called Circle Justice.
Edwin—He is one of the Native Americans in charge of Circle Justice.
It’s not surprise that isolation would become a central theme to the book since Cole is put on an island alone to work out his problems. The ideal goal for Cole is to reflect on his actions and reenter society as a changed person. Isolation is explored in several ways—mostly through Cole’s experiences.
 First, Cole feels social isolation from the community. For example, Cole believes that people in his community try to help him be a better person only because they want to get rid of him. Mikaelsen writes, “He hated their fake concern. They didn't really care what happened to him. They were gutless—he could see it in their eyes. They were afraid, glad to be rid of him. They pretended to help only because they didn't know what else to do.” Do you see how Cole is isolated from society? He does it to himself, but his community also pushes him away too.
Second, Cole experiences physical isolation. He is physically placed on an island alone. The separation from others really gets to him. Mikaelsen says, “Some nights he cried himself to sleep from loneliness. He couldn't help it. The silence became overpowering, and he longed to hear another human voice.” It’s not that Cole even wants to interact with others; he just wants to hear them to know that he isn’t alone. 
Isolation persists throughout the book until the end when Cole returns to society. From there, he must use his new skills to reenter his community.

While the "circle" theme (or, "karma") is a great and prominent theme in Mikaelsen's Touching Spirit Bear (as outlined above), there are also a myriad of other themes Mikaelsen weaves through his narrative that are worthy of exploration.
Healing is a major theme of the novel. The urge and necessity to "heal" spans across dimensions, both physical and spiritual. Some textual examples are:

Cole's initial assault on Peter. This attack is a necessary step towards healing, and is a physical and spiritual endurance on both characters thereafter.

When the Spirit Bear attacks Cole. This instance explores Cole's pain and path to healing that parallels his initial assault on Peter.

Edwin and Gavey's atonement for their past sins. This highlights a prominent struggle towards peace that promotes healing.

Cole's Mother, and her broken heart. In "letting go" of her troubled marriage, Cole's Mother embarks on a very tenuous path to healing.
Along with healing, comes forgiveness. This is another theme Mikaelsen explores, and almost works hand-in-hand with "healing". Each of the examples above insight pain, healing, and forgiveness as the ultimate goal. A vital asset in healing is forgiveness, and each character is on their own path towards enlightenment.
In choosing a theme above (or creating your own) I'd advise you to consider which theme speaks to you, and investigate your own reasoning into why the author uses this theme. This will help you create a strong thesis statement and argument.

There are several wonderful themes in Ben Mikaelsen's novel. Touching Spirit Bear. 
One dominate symbol and theme in the novel is the circle and traveling in circles. In literature, circles can mean wholeness or healing.  Cole Matthew's life moves in a full circle as he is sent to the Alaskan island as a 15-year old juvenile delinquent who assaulted a boy for telling on him and later returning to the island and living with Peter Driscal, the boy he assaulted.
Some additional textual evidence of circles as a theme are:
Cole keeps getting himself in trouble and his parents and their high-priced lawyers usually rescue him.
Cole burns down the hut and later rebuilds it.
Cole continuously tries to swim off the island, running from his problems, only to return to the island to complete his healing.
Through flashbacks, Mikaelsen shows events that led Cole to being on the island and how his parents' actions contributed.  Later during physical therapy he reconciles with his mother.
Cole blames everyone for his anger and later learns to forgive.
Peter beats up on Cole in anger and later heals
Cole and Peter carve a circle symbol as the last symbol on the totem pole symbolizing their healing.