I really wanna to update the maps and the Book of Monsters (rock version i guess) is somewhat helpful but ultimately vague. I bough the character info book and i feel like maybe wasn't worth it.

Like Pocket Power (for spells and map), World of Nexo Knights Heroes, & Knight's Code seems to be the only worthwhile things worth buying to help update the wikia, while Books of Monsters is decent, actual info on Wanda was nice. I haven't read all of the character enyclopedia just yet but it wasn't what i was hoping for. But the clay minifigure is nice.

If not the handbook - any suggestion on what nexo knight stuff i should keep an eye on buying to help update the maps?

Because it almost takes a lot of guess work because World of Nexo Knights had names but literally didn't diffieriate between where said town/city was. I have literally no idea where the wooden forest would be. Near the swamp? Probably but that mean rewatching and that can take a good while. I have to do it anyway to list every town mentioned since the OTHER map listing is somewhat outdated.