First Zaregoto and now this, it pains me to read stuff that are kind of underrated, at the very least in the west. The manga has only 5 thousand members as of today, yet a lot of generic stuff has so many :(.
Anyway my point is, it is that good, I loved Excel Saga's manga, and it being underrated should, by no means, stop people from reading it. Probably as many other people, I know Excel Saga because of the anime. I rewatched the anime while reading this and honestly, the anime's story isn't that good in comparison, so I think what I really liked about it, was the characters. (and surprisingly I preferred the spanish dubs rather than the subs)
The manga is so much interesting! It starts off pretty slow, with the usual shenanigans the anime had, having the usual plan of domination of the day for it to fail, and then repeat. After a while, it starts moving on into a different direction, in which you just can't stop reading. It keeps hitting you with so many mysteries which honestly I thought some were gonna be explained not so late, but actually almost all answers are in the final volume.
It's really far from generic to be honest, and even if it's 27 volumes, like another review says, Excel Saga has a LOT of dialogue, so it might be hard to get into it at first, I may have skipped a few things Excel said, specially since she uses a lot of words from other languages.
I really recommend it, although I can't quite pinpoint what kind of genre this is, and to who I should recommend it. Someone say it's more of a political satire, but honestly that just sounds more boring than what it actually does. It's mostly action/comedy/sci-fi, but some times it goes thought different phases. You have to read it for yourself to understand it.