Tnx for the scan. I think I was about to commission that but you got it first. Although the scan is... errr... well, it could be done a bit better, you know? That's way too gray. Not to rant, thanks for buying and scanning it, just saying.
This scan is not too bad and its darkness is not merely the fault of the scanning hardware. I believe that this scan can be brightened easily by cleaning it with photoshop. Here are some examples of edits. I can edit the rest of the book like this if you want. Please note that the edits have some of the shading destroyed but I can add that shading back in. I only made these as quick samples to show how they can be cleaned and I can improve them more later if requested.