Lets put it this way...

Negi, as many characters, starts being an 'innocent genius' (ok... not so many). But the passing of the series makes him mature more than he should be at his age. His magic does increase... how much? you must read to find out.

Most of the girls are 14. So the harem side of the story isn't as deep as it was on Love Hina. But whenever it is introduced, it is well balanced. It ain't borderly ridiculous as it was sometimes in Love Hina however.

Are there plots twists? Hundreds of them.

Villains? Yep. Some likeable, some surprising.

This manga is by far the best manga Akamatsu Ken has ever done. Several of the initial chapters are light and somewhat... common. But the story starts to become more interesting when they enter the Library arc... followed by the Eva and Kyoto arcs. Festival arc is somewhat overwhelming and fantastic as well.

Can't say more without entering spoiler area...

Read it.

PS: NEVER touch the anime series. They are crap. The only 'good' adaptations are the recent ova. But they portray arcs beyond volume 25