There are basically two types of movie soundtrack album. There are the ones where you get a song from the opening titles, a song from the closing titles and 10 tracks of incidental music or, alternately, the ones where a movie is set in a specific period and the sountrack is a "greatest hits" of that period.
This breaks the mold. Instead of 15 tracks of inoffensive incidental music designed not to detract from the movie (and hence, be pretty forgettable) someone had the ingenious idea of throwing Eddie Vedder, a guitar, a banjo and a mandolin into a recording studio and using the results.
The results are an album that stands up in its own right as a great record and a superb soundtrack. The simple chord sequences, evocative lyrics and Vedder's superb voice perfectly encapsulate the excitment and loneliness of the wilderness and the disillusioment that might lead someone to choose that over society.
Despite being better known for Pearl Jam's rock music, the standout tracks on this album are the simplest: those that use an arrangement of guitar/mandolin and Vedder's haunting delivery (Society, Rise, Long Nights).
If you're looking for something epic, this probably isn't the place, as each song clocks in at about 2 minutes. However, each short track is perfectly formed and results in a record that I would highly recommend.