its worth picking up a copy of the Chrismar map, to use as a backup map and to cross check for portages  - of course, if you want to be really up to date, you would have to buy one every few years I guess.

"official" as far as the one the park recommends - not sure if they have any actual connection to the production of the map or not, but it is supposedly the most up to date. its a bigger scale than the Fisher maps, so less detail, but you could navigate the park with just that map - folds up about like a standard sized road map.  I do use it for cross checking portages against my old fisher maps (some of which are near 30 years old and portages are out of date in some cases) - but I have a lighter map I bring as backup that is also quasi official