Extraplanar sourcebooks have always hit that sense of wonder for me since the original Manual of the Planes. There's something about the strange and alien worlds coming to life that makes me want to go there.3e Manual of the Planes
4e The Plane Above
What about you?
I agree that Night's Black Agents adventures do not fit the pattern that the rulebook tries to set up. But guaranteed success on a skill check - especially when combined with ability refreshes - is great for high action.Night’s Black Agents - all the adventures READ fantastically (particular shout-out to The Persephone Extraction), though I am dubious about how well they play
Esoterrorists - the Worldbreaker mega-adventure - similar to the above, reads great, but the Gumshoe system fights against being used for high action
Esoterrorists - the Worldbreaker mega-adventure - similar to the above, reads great, but the Gumshoe system fights against being used for high action

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.