Wanting to do a custom binding of the book series, looking for help.

I was inspired by a post here a while back about someone who did something similar and I'd like to try my hand at book binding. I've purchased the first three books, but I'd like to do a custom binding of this incredible series. My plan is to do leather bound volumes of three novels at a time and to have them be a bit larger than the paper backs (think something akin to D&D player manual size) complete with metal bound corners, lots of charms, claws and such and a nice leather book mark. The problem is I don't even really know where to start!

I've visited r/bookbinding and there are plenty of guides for me to get started (I'm going to do a test run to create a few notebooks for me to practice) and places to buy supplies. The bigger question I have is: Do publishers allow readers to do such a thing, and, if so, where can I get the texts in an editable format so I can adjust them to my planned size?

Thanks you guys!