Spruce it up with a nice layout. Hire an artist to add a few more illustrations to the first part of the book, as well as color in the existing art (if you plan on publishing the book in color, that is). Expand the bestiary to perhaps two or three times its present size, and maybe add a bit more meat for the game master.

Otherwise, you wouldn't have to change very much from the existing .pdf. The game itself, after all, has spent a decade evolving.

I'd be happy to pay $30 US for what I describe. :-)

Couple of things:
- grid-aligned lines (i.e. lines in parallel columns on same height), it is documented that increases speed search
- would be nice if the rule examples were less emphasized visually then more than, as is now (in comparison to the rest of the text). Examples are less important than the rules themselves, aren't they?
- i think i understand the font choice, but there are loads of more readable ones.
- alternate table row hue seems a better choice than the existing gradient...
- color overall mismatch

I know I'm nitpicking, but I hope you'll appreciate the effort.