This much earlier work (written in1909) does not yet have the deep classical narrative found in Undset's later works, but it is still a wonderful read. Exploring themes of lust, love, revenge, and motherhood the novel certainly does not shy away from heavy lifting. While Undset's later Norwegian sagas are set at the height of Catholicism in Medieval Norway, Gunnar's Daughter is set a bit earlier, just as the new faith is taking hold. Undset does a fine job conveying the time. Still finding her footing as a formidable descriptive narrator, this novel is much shorter and a quicker read than the later series, but well worth a gander.
Due to more adult situations and themes, I would recommend Gunnar's Daughter to older teens and adults.