This is one of my favorite rulebooks I own. It develops the setting very well, having a distinct feel and character about it that translates into the rules very effectively.
The rules seem haphazardly placed. Once you figure out the rules and wrap your head around them, they are intuitive, but actually finding everything is not easy.
Some rules are poorly translated. Key examples would be the ability berserker and how it interacts with defense stat substitutions; references in abilities like loremaster (referencing activating artifacts) that don't actually reference anything; and the organization of spells and rituals where they inconsistently reference their schools of tradition.
Additionally, abilities aren't worded consistently- you frequently have to make logical jumps as to which parts of an ability upgrade override the previous level or not, which parts are overridden, how the ability interacts with other abilities, and we frequently encounter damage bonuses that we have to decide when to apply the damage bonus and when not to. For example, robust, worded very specificly vs berserker which isn't clear whether the bonus damage applies to only one hit per turn or every attack or if it applies to only one attack when the character makes multiple attacks on their turn and then also to attacks of opportunity; and then beastlore vs leader, where one states the character deals a bonus die of damage against a specific monster and the other states all attacks against the target- is that intended to keep dual wielders from abusing the bonus beastlore damage but still allowing the bonus to apply to attacks of opportunity?
While these seem like minor issues, they can be argument causing because of disagreements as to how said rules are meant to be read. Some clarification definitely needs to be made inside of the rules.
Finally, frequently important rule clarifications are found inside of the flavor text instead of in the ruleblock of the ability, which causes some referencing issues.
Despite my complaints, I still feel like this is a 5 star book and ruleset. The art is beautiful. The setting is well made, explaining enough to wet a DM or lore loving player's appetite, while leaving enough open so that the DM can make their own additions to the world without getting in the way of established lore. The rules actually mesh with the setting really well. They help create a game where character death is just around the corner but not unavoidable. They make DMing a simpler task than other systems, putting all of the rolls in the players hands and it rewards prep work and encourages building a sandbox, since there is no linear scaling with player advancement.