Got sent a copy of Island of the Necromancer recently. It's not great, but the first half of the book is a free form romp around the island of Sholani, poking things and hoovering up anything you can carry. Easy thing to map, I thought, so I did.
First thing I noticed though, was that it totally disagreed with the new maps by the original cartographer; Sholani is not 100 miles across, as the map suggests. The book was quite clear about times and distances, and mine more or less accurately reflects that. Still, can't hold it against them. Mapping Titan accurately is mental.
It's nice to see the patchy and confusing text take shape into an actual map. In classic FF "you're not the boss of me, I'll do what I want" style, there's a swamp next to a desert on an island the size of Cambridge. Which is fine. Interestingly, I think the whole island is U shaped in its east/west profile, with swamps and bays in the middle and cliffs on the top and bottom.
Next step is to add in all the surprise elements that the players shouldn't automatically know about and run a little hex crawl on it. Minus all the maths puzzles, of course.