So why only 4 stars? For me, there was a lot of building in this, but it didn't build to anything hugely meaningful. Dalinar's flashbacks were cool, but they lacked the surprise of Shallan's backstory (in Words of Radiance) or the emotional intensity of Kaladin's past (in The Way of Kings). While Dalinar is critical to some key events in the book, he felt oddly removed from the narrative in some portions, particularly around part 4.
My other minor gripe was with the 'The eagles are here!' moments throughout. In the previous book, Words of Radiance, there's an epic scene where (spoiler) Kaladin overcomes huge adversity and swears to protect a man he has incredibly good reasons to hate, in the process gaining new magic powers (end spoiler). There's several of these scenes in Oathbringer, where the characters look like they're about to be defeated ... and then they swear one of the Ideals of the Knights Radiant (a order of magical warrior), gaining them just the right amount of power to triumph. I wouldn't have minded if there was only one or two moments like these, but it did feel like this particular technique was overused.
Now, my review might sound overly negative. I assure you, I deeply enjoyed this book and I get what Sanderson was trying to achieve. As book 3 out of 5 books in the first phase of the Stormlight Archive, there needed to be a lot of set up and world building for the next two books to make sense. And boy - the world building in this is incredible, taking us into places we've never seen in Roshar. The characters all get fantastic opportunities to develop and interact with each other. There's twists, and amazing fights, and a nice spread of POVs that captures the intense scale of the story from every angle.
When I say, then, that it's the weakest of the series so far, it's still a cut above pretty much everything else I read. In The Way of Kings and Words of Radiance, however, it has stiff competition! I'm incredibly eager for the next book, which comes out later this year. Journey before destination!