oh, and the bonus will multiply what you have as a current percentage before you level up. Therefore, 99% before lvl-up is actually the best thing you can have. However, do not "overforce" 99%, once you reach it-be sure to hold it there. I remember a time when I got no bonus. I can only hasard a guess that although it said 99% on my char-page, the database actually contained something close to 99.99 magic skill and considered it 100%. I was kind of upset.:)

What I can account for with numerical data though: I started constructing with Mia at lvl 36. I maintained lvl+4 magic skill on each levelup, with a 66-67% extra on skill. I did 1/3 of the level on TA armies, going to 99% skill. Then I built 2/3 of each level, and on levelup, I dropped back to +3 magic, but from 99% I got to 166-167%, therefore back to +4. I kept building till about lvl 42-43.

This is no secret, I was commenting on this all too often in chat. 2 days ago when Mia levelled up, I resorted to stealing and even digging to maintain 99% on levelups. 

On the numerical data, I hardly ever made precise testing, but I've monitored percentage changes in levelups for the last 20-30 levels of my two mages(they can be found in the hun-topic). I realised +66%, +79%, +28% rises which I can suddenly remember. Of course, this rate decreases the higher magic you have. The "par value" of plus magic for your level is lvl/10. This means that for a level 45-54 mage, +5 magic skill is an average, for 55-64 mage it's +6. If you can hold on to a lower-than-"par" skill, your bonus will be much higher from my experience.

Addendum:  I think my previous analysis was correct, but the conclusion was wrong.  I now believe that it should be benficial to hold magic at 99% when close to gaining an experience level.  Someone please save me from this mental torture!

I think Veriac provides an answer here to a question I have seen in a number of threads, and been wondering about.  The magic "bonus" achieved on leveling is the application of a conversion rate from level+X magic to level + (X-1) magic.  For example, lets say you are at magic level= exp level+4 and 95% of the  way towards +5.  When you level, the 95% is converted to the appropriate % towards +4 since your exp level has increased but magic level has not.  This often results in an apparent "bonus" in magical skill.  The formula Veriac quoted would result in a beneficial conversion of 10x your prior progress, but of course there would be a coincident effect that the new higher level has more "expensive" magic levels than the old.  From other discussions I gather that the mana usage requirement for magic leveling varies from level to level, this would explain the non-uniform results, i.e. sometimes you get a big "bonus", other times not.  Long story short (too late), no benefit to hold at 99% to get your "bonus", there is no bonus.  What say Ye, Veriac?

To add to that, when you level, you get some bonus "mana xp." I think it's for character class balancing purposes.

if 

x

 is the amount of mana used to increase your magic level by 1 above your experience level.....

Level+2 is 10x
level+3 is 100x
Level+4 is 1,000x
Level+5 is 10,000x

etc

Thats the reason why it slows down so much

r u sure that you get the points if you don't kill the monster? I thought that I tested this and found that you must kill it. could be wrong though. 

Bel'al

Or jsut fight a couple hundred monsters and run before you kill them :p

Thx and I also had a thought. Since Your magic level goes up  according to the manapoints used, If you did 4.8 trillion homeports or made 3.8 Billion magic weapons, you could concievably raise your Magic level much higher than your level. Of course who has the clicks and time to do that. It would just be a fun experiment. After three years or so, someone could have the most powerful level 20 Mage ever. 

Bel'al

As you hit the middle levels (25-32) you will see your magic jump up a few more levels passed you experience level.