Gear that adds to a Knowledge skill.

[Paragon]

In the Broken Earth setting, one of the things you can get are reference books that add to a particular Knowledge skill. Now, part of this is just a limited version of the Scholar Edge (since it only adds +1 and to one Knowledge) without the per-requisits and on a piece of gear. However there are a couple of issues I thought I'd ask about.

1. It needs to have some method of handling cases where the person doesn't have the Knowledge; what it should probably do is nothing, but I wanted to make sure how I'd set that up rather than get an error message.

2. What will the program do if someone has two copies of the same book? Is there a method to prevent any problems here (I don't think they'd stack, though the note is pretty terse).

Come to think of it, the books that add +1 to Survival might have an issue with either of these, too.

Any help would be appreciated.