Great to see Isengard's Spell Book reworked. It's looking lovely and the revamp makes a lot of spells more appealing. I have some feedback and questions too:
The Vision of the Palantir spell now serves a clear role in the early game separated from the Crebain upgrade bought at the Citadel: great way of dividing these.
The Tainted Land spell I agree works much better with Isengard than in Mordor: it seems Saruman had much greater influence on the lands in less time than Sauron ever did in Mordor. This direct implementation of fast extension of defertilised land fits well with Isengard's concept of a growing industry.
When I wondered for myself what changes would be made in the Spell Books, I thought there might be a way to combine the spells of Devastation and Tainted Land, since they share the thematic of destroying nature, but then the strategic uses of the two spells differ significantly, so you made the right choice for balance over theme.
Regarding Saruman of Many Colours I am quite confused as it seems the power is barely improved but costs 3 Points more, whereas Gandalf the White in Gondor is improved much more and costs only 1 point more. I think their power should be similar, unless Saruman is already stronger than Gandalf the Grey, making both Spell upgrades rather a way of equalising their strengths.
I also find the description not suiting, since it is only implied in the movies that Saruman is doing Sauron's dirty work. In the books his motivations are much clearer, trying to find the One Ring for himself and rule all over Middle-Earth, and he defies the Nazgul when they have come to get rapport by lying to them about his knowledge of the Shire and Gandalf. Anyhow, some interpretations regarding the 'Many Colours' aspect see it rather that in an attempt to be all-powerful Saruman loses his pure white robe, which symbolises his blurred intentions. I would like to see the change of description more fitting to the lore of the books over the movies.
About the Fuel the Fires Spell, I already read in the German feedback that the spawned Lumbermill will come with the resource upgrade (that is, in the new system I assume it counts as an external build plot?). Does this spell mean that Lumbermills can no longer be bought at Settlement plots, and what will happen to the bonus of cost reduction of buildings?
The spell Minions of the White Hand is an equally interesting renovation and certainly very unique, having three kinds of weak summons rather than one strong one. I assume the role of the Warg Archers was questionable anyway, when players rather used them for their trample abilities. The mounted Traitors of Rohan form a proper alternative here. I like the looks of the Wildmen Plunderers, are they the same as when regular Wildmen get their Heavy Armour upgrade (have to admit I never got Wulfgar to level 10
)?
Then, another question, does Grishnack only spawn with his orcs or also with the other summons? I also wanted to point out that Isengard has many options to deal with heroes, how do you see Grishnack stands out and differs from the existing options?
The central spell is another fantastic solution that displays the importance of the Wizard Saruman and Orthanc itself. I agree completely with your reasoning towards not putting an economic spell or the Many Colours spell in its place. I do have to ask about the upgrades though: as they are free and all Citadels on the map can be applied without costs, the cooldown should be very long for the sake of balance. How is this addressed I wonder?
Lastly, the Isengard Unleashed spell shows a feat of sharp observation within a clever system. I believe it is proof of how much the Edain Mod has a clearly structured ideology in which functionality has the highest importance; the boundaries you have set do not reduce freedom, they rather enforce creativity!
Great job, looking forward to Rohan and the other faction spellbooks. Hearing about them and providing feedback makes me almost happier than using them in-game