Can you max out the skill tree?

[Hegemon]

I ended up with 2 skills not upgraded at the end of the game. Is it supposed to be this way or did I miss something?

You max out your character level at 28 giving you 27 upgrade points. I found 4 upgrade kits (booklets) for another 4 points, thus having a total of 31 points. You would need 33 points to upgrade everything. Did I miss some upgrade kits or is it designed this way?

[Hayate89]

There are 6 upgrade books to find :)

[Hegemon]

So I missed two... I thought I was being thorough, apparently not thorough enough. Thanks for clarifying.