So I woke up at 3 AM the other morning, and finding myself time for philosophical speculation, it occurred to me to wonder what would happen if you put your hands on two linking books at once. Or, could you use four books to draw and quarter someone?

Maybe they would cancel each other out, or short circuit given the unintended flow?

Yes, maybe there's some kind of safety feature written in.

You would like to think so, given you don't want the drawn and quartered scenario (at least not accidentally!).
While it is hard to imagine you would try and use two books at once, perhaps if a book senses that anywhere in the circuit between you and it there is another book, it simply won't work. A bit like an electrical circuit tripping rather than blowing up everything connected.
FYI that is a far more interesting musing at 3am than most of mine

The Linking Books are half of the equation and are dependent on the Descriptive Books that give all the details of an Age. That process seems to be somewhat self-governing. You can have multiple linking books for an Age, but only one Descriptive Book. While it's not expressly stated in the lore of Myst, I believe that rather than being "pulled" into an Age, a path is created and you materialize there. So, I would guess that the operation of the books are to transport a whole being to and from an Age. If there is an overlap, whatever mechanism governs that process would probably prevent the action until you were only touching a single panel.

That's so cool TM

OK, I put my hands on two linking books yesterday and didn't go anywhere!

flotsam! Thank goodness you weren't transported in oblivion!