The goal is to provide a reading that is as brisk as possible while still providing a thoroughly detailed understanding of the story events in each volume. What I specifically try to avoid doing is covering character interaction in great detail. There are two reasons why. One is because doing so is an incredibly easy way to end up with an unnecessarily bloated summary. The other is that character interaction is the series' greatest strength, and arguably what you're really here for, and I don't want to spoil that.
So, why am I starting at volume 4? Because the idea to do this didn't occur to me until I was reading that volume. Then, without further ado:
Having learned from the chronicler in Kumersun (who was secretly a giant bird spirit) that there is a friar up north who collected pagan tales and might be able to tell them more about Holo and Yoitsu, Lawrence and Holo head north. They first stop in at the town of Enberch, where after asking around they are directed to a small village further up the road called Tereo. Arriving in Tereo, the two meet a young miller named Evan, and a young priest named Elsa. As they ask around, Lawrence and Holo find that the villagers are reluctant to say anything about the friar and his abbey, and also learn that Tereo's relationship with Enberch is strained. The tensions originate from Tereo's worship of a pagan god--a large serpent known as Lord Truyeo--which is heavily frowned upon by the Church in Enburch, and somewhat antagonizing due to the presence of a church (run by Elsa) in Tereo. Tereo is able to get away with worshipping Truyeo, however, because Elsa's predecessor, Father Franz, was very well-connected and able to stave off accusations of heresy. To further complicate matters, Father Franz was able to negotiate an extremely favorable wheat-selling contract between Tereo and Enberch that allowed Tereo to essentially name its price when it came to sell the harvest. Father Franz has passed away however, and Elsa has been unable to garner any of the trust and support that he possessed.
In the process of learning all of this, Lawrence comes to the realization that the friar he was told of in Kumersun was likely Father Franz, and that the church in Tereo was his "abbey." As such, he and Holo confront Elsa and convince her to give them access to Father Franz's extensive records of pagan legends. It turns out that despite being a man of God, Father Franz was a thorough researcher of pagan religion, a fact that causes Elsa to question her own beliefs somewhat.
The tenuous political and religious situation in Tereo makes Lawrence uneasy, but Father Franz's collection is quite extensive, so he and Holo decide to stay for some time to read through it and search for any leads on Yoitsu's fate or whereabouts. However, while they are reading through these records, the Tereo-Enberch situation falls apart; a messenger arrives, informing the villagers that someone has died from the wheat Tereo sold Enberch, and in all likelihood a messenger will arrive at dawn demanding that Tereo refund the entire harvest. For the villagers of Tereo, who have grown complacent and lazy off of the comfortable agreement Father Franz secured for them, this is an incredible crisis. Furthermore, Lawrence suspects that he and Holo will be the first ones on the chopping block, as travelers are always the first to be suspected in times of trouble, and their arrival in Tereo coincided closely with this event. Lawrence also realizes that even if he and Holo were to escape, the villagers would only focus their anger on Evan and Elsa instead, who have also been the subject of constant distrust (Evan because he's a miller, Elsa because she operates a church in a pagan village).
Unable to figure out a solution to Tereo's problem, Lawrence decides that the only way he and Holo will get through this alive is to cut their losses and flee, using Holo's wolf form. They offer to bring Elsa and Evan with them, but before they can fully leave the region, the priest and miller decide to return to Tereo, Elsa to offer her assistance, despite knowing full well she would likely just be scorned and executed, and Evan to protect Elsa. Once again alone with Holo, Lawrence finally comes up with a plan to turn the situation around in Tereo. They catch up with Elsa and Evan, and the four sneak back into Tereo to enact Lawrence's plan.
In Tereo, a procession from Enberch has arrived, consisting of wagons containing Tereo's wheat to be returned, Riendott (a wheat seller that Lawrence met in Enbirch), and to Lawrence's mild surprise, Bishop Van. Lawrence surmises that Enberch plans to use this opportunity to not only dismantle Father Franz's contract and subjugate Tereo financially, but to accuse the village of heresy and force them to convert fully. Lawrence, Holo, Elsa, and Evan reveal themselves in the village square, to everyone's surprise. Having reconciled her own beliefs about God and Truyeo, Elsa confronts Bishop Van, and makes the bold claim that Lord Truyeo is one of God's creations. This would thus prevent the Church from denying Truyeo's existence. Elsa proves this with a miracle: Holo discreetly causes the wheat in the wagons to grow instantaneously, stunning everyone except for Lawrence and co. Unable to deny Elsa's proclamation, Bishop Van agrees to recognize Truyeo as legitimate.
With the religious problem solved, Lawrence then confronts Riendott about the returned wheat. Coming to the conclusion that Riendott set Lawrence and Holo up as scapegoats, and that the report of someone dying from the wheat was likely a myth, Lawrence presses Riendott into accepting a reduced refund on the wheat, knowing that the merchant would prefer to avoid having his treachery exposed, particularly in front of the villagers. He also persuades Bishop Van to allow Tereo to sell wheat under his name. Lawrence also dismantles Father Franz's agreement. Though the villagers are initially dismayed and outraged by this, Lawrence reasons that the agreement was a source of resentment for Enberch, and as long as it remained there was no guarantee that something like this would not happen again in the future. Instead, Lawrence teaches the villagers how to make cookies, which he noticed were completely unheard of in the northern lands. The cookies sell extremely well due to their uniqueness, but Lawrence knows that others will soon copy Tereo. By giving them this leg up however, he hopes that the villagers will have the tools to be self-sustaining, rather than relying on Father Franz's agreement. With Elsa finally gaining acceptance from the village, and Evan stepping up to handle negotiations between Enbirch and Tereo, Lawrence and Holo pack up and set out for Lenos, a town where legends of Holo are said to still exist today.
And there you have it. Keep in mind, to anime-only watches this is kind of a "lost arc", you could say. It takes place between the Amati arc and the Lenos arc.