Yes, I found that terrain issues can really mess up a game. I destroyed some opponent's city by raising a volcano on it, and it turned out that it was the only way towards that guy's other cities. And that huge peninsula he was on didn't have any beaches. The Terraforming spellbook would have been very usefull, but it's not researchable. I think the Terraforming, Enchantment, Combat and Mobility spellbooks should be researchable, but more research-expensive then the elemental ones.
