Estou à procura de uma série que li no ensino médio nos anos 90 sobre um mundo onde as pessoas tinham uma habilidade mágica e as palavras eram literais

Isso é quase certamente a série Xanth de Piers Anthony, atualmente com cerca de 41 livros.

Each human character in Xanth is born with a unique magical ability, called a talent. With the exception of the curse fiends, the winged centaurs, and the child Surprise Golem (Daughter of Rapunzel and Grundy Golem), these abilities never repeat exactly in individuals throughout the entire history of Xanth (although nearly identical talents show up on occasion.) Though many talents are limited in scope (called the "spot-on-a-wall" variety), the series focuses mainly on individuals with "Magician" caliber abilities (one of the criteria for serving as King of Xanth).

...

Many of Xanth's other geographical features are puns on those of Florida (for example, Lake Ogre-Chobee and the Kiss-Mee River). The Florida Keys also exist, though they are, in Xanth, actual keys. Other punnish features include the Isle of View ("I love you"), Mount Ever-Rest (Mount Everest) and the Centaur Aisle (center aisle) created by a magician from the Centaur Isle. The moon is close enough that flying creatures may land there; the back side is sweet and honeyish, the visible side has turned sour and become curdled cheese, due to observing what has happened on Earth and Xanth. Plants may bear fruit of all descriptions (pie trees and shoe trees are common) or they may be carnivorous (such as the tangle trees), making travel in Xanth risky.

Yet the higher growths were no more promising; the huge metal trunks of ironwood trees crowded against the burned-out boles of ash. Rust and ashes coated the ground around them.
_{The Magic of Xanth: The Source of the Magic, chapter 7: "Deadly Distaffs"}

Quando li esta pergunta, a primeira coisa em que pensei foi A Magia de Xanth , de Piers Anthony .

Aqui está a capa do primeiro livro, Um Feitiço para Camaleão :

De Wikipedia :

Xanth (/ˈzænθ/ ZANTH) is a fantasy world created by author Piers Anthony for his Xanth series of novels, also known as The Magic of Xanth. Anthony originally intended for Xanth to be a trilogy, and after the success of the first three books expanded the series to nine books. A devoted fan base persuaded the author to continue writing the series, which is now open-ended.

Cada personagem nos livros tem um single, único poder , que ninguém nunca teve antes ou será novamente, embora os poderes possam se sobrepor.

E as coisas no livro são definitivamente como você descreveu - o nome literal. Aqui está o Ironwood:

Yet the higher growths were no more promising; the huge metal trunks of ironwood trees crowded against the burned-out boles of ash. Rust and ashes coated the ground around them.
_{The Magic of Xanth: The Source of the Magic, chapter 7: "Deadly Distaffs"}