Now, after watching the rather interesting intro video, the first thing you notice about the game is the attention to detail: The menu is very nicely presented, and the campaign menu presents a very satisfying faction choice with nice descriptions, nice presentation, and a delicious-looking campaign map which just makes you want to start straight away. The factions themselves are very interesting, and it's here where the true advantage of this mod presents itself: Where else, for example, can you play as such a faction as Navarre? This is a faction which is deemed insignificant today, but was at the forefront of politics during the Hundred Years War. Historical accuracy seems to have been tied in with a small campaign map which favours detail and immersion over quantity and notions of grandeur. Upon starting a campaign, I note the strung out possessions of all the factions, such as the "Duché d'Alençon", a landlocked province surrounded by France yet owned by Navarre. Playing as this faction, I'm at once immersed, debating how I can keep this small state alive. I have a decent income and a large army, but it is composed mainly of light troops, and my forces in northern France are held down by general unrest amongst the population. Should I attack the French to expand my dispersed French territories and unite them by capturing Caen? Or should I use those lands merely as a bank in order to fund campaigns against the Castilian threat to my west? Lots of decisions to make...I like it!
Similarly, while starting a French campaign, I am stunned by the extent of my domains and the detail invested in creating the Royaume de France's territory. Zooming in as much as possible, you realize that this is how Total War is at its best: It's not one of those ridiculously ambitious mods where the whole of France is perhaps four of five regions (or in Empire, one) in which you don't even care about your lands, where they're just a flat green background for the cities you use to build/spend/recruit. In La Guerre de Cent Ans, however, you truly feel like a medieval French king, ruling over a heterogenous mass of vassals and their provincial lands. Chateaux are hidden away amongst small rivers, valleys and woods, and moving your troops around looks more like something from the Lord of the Rings than an abstract, dull, chess-game you can quite easily get used to playing other TW games/mods.
Interest is easily maintained alone by this immersion: You make plans that seem more realistic than the 'arcade' version of rampaging around Europe with a few stacks. Each small town and fortress you seize, despite being puny in the overall territory of Europe, feels like a step in a Great Game you are playing to slowly expand your land and prestige. No longer will you see 'The Holy Roman Empire being brought to greatness by conquering France, Spain and England' or other silly phenomena. This is a small, focused arena where conquering half of France is a massive achievement in its own right (if you're doing this as the English, you get the accomplishment of recreating the expansion of Henry II or Henry V over a long period of time, unlike in vanilla where it's a matter of winning a couple battles. Feels good man
There is a greater focus on sieges, which increases the medieval theme of the game, and making campaign plans takes time and effort: You have to take internal stability, the loyalty of the nobility, and the strategic locations of recruiting centres (castles) into greater account while making these lengthy preparations. For example, playing as the French, I wish to destroy the English presence in Aquitaine, and yet rebellion and unrest in the South means that I have to alter my plans: Drawing knights together from various corners of the kingdom and supplementing them with solid numbers of men-at-arms, I commence a lengthy Royal Progress to re-assert royal authority in the rebellious lands of the South. It is a lengthy procedure, rather than just taking a single town and exterminating it before setting off again to fight another nation. Likewise, as the English, I have many affairs to deal with, such as massive unrest in Aquitaine and French soldiers massing at the border, impending Scottish invasion (one of the many welcome scripted events) and rebels at home.