Simple, Detailed
Speare wastes no time in telling this story. Her word choice is simple and direct, with very few fancy pants words to muddy up the way.
However, her simplicity does not skimp on detail. Speare did her survival homework, and it shows in the details about everything from building a log cabin to loading a rifle to building a snare. She could probably write How to Survive in 18th-Century Maine for Dummies if she really wanted to. Take this description of stringing a bow for example:
Carefully, Attean skimmed off the drops of oil that had risen to the surface [of Matt's fish stew]. He rubbed the oil from one end of the boy to the other till the bare wood glistened. Matt's frayed bit of string he cast aside. Instead he set about making a bowstring as he had made the snare, of long strands of spruce root. This took most of the morning as he patiently twisted the strands together, rolling them against his thigh to make them even and smooth.
Finally he ties one end to a notch in the bow and began slowly to bend the wood. […] It seemed impossible that it would bend, but slowly it yielded, till the string slipped over the notch at the other end. The bow was finished. (12.10-11)
The words may be simple, but the picture Speare paints is still super detailed.