GetBackers is a fun manga, but, in my opinion, is actually more accessible in anime form.
The manga art is unusually hard to follow - particularly in fight scenes, and especially in the first five volumes or so, I would have had a hard time figuring out what was going on if I hadn't already seen the anime. And the plot and content of the anime follows the manga relatively closely; you aren't missing a lot by restricting yourself just to the anime series, if you choose.
And, actually, this is not a series I'd recommend to people who don't read manga regularly. It has a lot of the manga conventions - the video-game style fight scenes and moves, chibis, etc. - that tend to turn people new to the genre off of manga.
But I enjoy the series a lot. Ban and Ginji are incredibly adorable and so very obviously doing it that even some of the official art has them in, like, wedding garb. (And we won't even talk about the slashiness of the secondary characters; Kazuki and Juubei are, as far as I can tell, canonically a couple.) The world is interesting, the characterizations are fun - basically, this series is reading candy for the manga inclined.