This, the final book in the tetralogy, is the best of all. None of them is stand-alone, so The Master of Hestviken must be considered a single work. It is an amazing and rich accomplishment from Sigrid Undset, with scores of characters and seven generations of the Olav Ribbung clan. I liked it only slightly less than Kristin Lavransdatter, which I consider Undset's masterpiece.

As others have commented, the main themes of the work are free will, sin, and redemption. From The Snake Pit:

So many a time had he allowed himself to be driven out of his road, upon false tracks that he had no desire to follow. Long ago he had acknowledged the truth of Bishop Torfinn's words: the man who is bent upon doing his own will shall surely see the day when he finds he has done that which he never willed. But he perceived that this kind of will was but a random shot, an arrow sent as a venture.--He still had his own inmost will, however, and it was as a sword. When he was called to Christianity, he had been given this free will, as the chieftain gives his man a sword when he makes him a knight. If he had shot away all his other weapons, marred them by ill use--this right to choose whether he would follow God or forsake Him remained a trusty blade, and his Lord would never strike it out of his hand. Though his faith and honour as a Christian were now stained like the misused sword of a traitor knight, God had not taken it from him; he might bear it still in the company of our Lord's enemies, or restore it kneeling to that Lord, who yet was ready to raise him to His bosom, greet him with the kiss of peace, and give him back his sword, cleansed and blessed.

From The Son Avenger:

The flaming terror that had caught his spirit had now burned itself out; he was tired and drab within. He was now on the way to do the thing from which his whole life had been a flight, and this time he knew he would do it; he knew this as surely as he had known all the other times that he would flee from it as soon as he saw a way out. But his soul was grey and cold as a corpse.

He had heard a thousand times that God's mercy is without bounds, and in secret he had relied on this: what he fled from was always there, waiting for him when he took courage to turn, since it was all that was outside time and change: God's arms spread out on the cross, ready to enfold him, grace streaming from the five wounds, the drooping head that looked down over all creation, watching and waiting, surrounded by Mary and all the saints with prayers that rose like incense from an unquenchable censer. His servants were ever ready with power to unlock his fetters; the Bread of Life was ever upon the altar. God was without bounds.

But he himself was not, he saw that now. It was too late, after all. The bounds that were in himself had set and hardened into stone--like the stones folk had shown him here and there about the country which had once been living beasts and men.

so much more happens with a larger cast of characters in this final chapter of the Hestviken saga that it's not as slow a read as the earlier books.
Impressive how Undset manages to make even the wretched Eirik sympathetic.

An enormously powerful story of sin, flight from God and the dark consequences thereof; and of grace, repentance and forgiveness. The final measure of God's justice is startling.

This is the most moving human tale I've ever read. After a (deliberate) period of desolation in part two and three (primarily the former) of the tetralogy, this rounded off in a wholly penetrating, unexpected, mystical, and mature way.

The way Eirik's character meets the end was a work of literary mastery.

This is the most Catholic and majestic work of fiction I've ever read. It's instantly my favourite. It has surpassed all others. Undset is amongst, and surpasses, the very best in her art.

I hope to meet her in heaven.

Deo gratias.

I'm honestly beset with so many different emotions at finishing this series. It would be amazing to discuss this in a seminar setting, for the intricacies to be unpacked. The course of Olav's life is bittersweet and the ending is not necessarily a happy one. Undset shows how the right path is always the best path, even if it is not the easiest-- we see how Olav regrets not taking it himself. The sheer terror that you see Olav go through in the last days of his life remind me of the horrors of Oedipus Rex and Othello.

A gripping and compelling story about this complex man, and his family’s dynamics. There are religious themes as well;once you start reading you want to finish.

This was the final installment of "The Master of Hestviken" series by Undset, who won the Nobel Prize for Literature in 1928. Norway in the 14th century is the setting, and the book completes the saga of the family of Olav Audonsson.

What an amazing series this was. Boy do I never want to get sent back in time to 13th C Norway. Brutal. Read this tetralogy if you can. Solid.

4.5 ⭐️

It is a gift. I have never read a better story of human sin and God's providential love.

Like her better-known masterpiece, Kristin Lavransdatter, The Master of Hestviken follows the protagonist (Olav Audunsson) through a lifetime and is matched but not exceeded in scope by classics like War & Peace or Les Miserables. Volume one deals with youth stepping into human responsibility and, with it, the tragic perpetration of grave evil; volume two sees life lived in maturity, well and badly; volume three watches Olav draw near to but decline the chance to repent for his youthful crime; and volume four shows him growing old in his sins, slowly crushing the humanity and love of God that had drawn him to repentance, and the powerful work of God's mercy upon him and his household nevertheless, where a kindness also done in his youth and often regretted becomes the means of his salvation.

Undset masterfully portrays people living their lives with careful planning, sometimes successful and sometimes undone by chance. Like the people we meet every day, the characters are loveable and frustrating. And over all hangs the mercy of God and the mystery of good and evil.

I finished this series of four books this year, when the fourth was released. I liked it even better than Kristin Lavransdatter. Undset deserved her Nobel Prize. She brings the setting of medieval Norway to life, and makes medieval life and ways of thinking feel natural and human. The story follows Olav from his youth to his old age, and she does each stage of his life masterfully. This last volume might be my favorite.

This whole series is rich, lush, amazing, deep and wide and high, transcendent…so so good. You should read it. Even better than Kristin Lavransdatter.