I really think this depends on what you intend to cover and what you want students to learn from it.
Do you hope for your students to work through the major parts of the books and develop a true appreciation for it? Good luck; you'll need to presume they already have a level of mathematical maturity and enthusiasm that is difficult to quantify and pin to a certain set of prerequisites.
Do you hope to inspire a group of not-necessarily-math-oriented folks to develop an appreciation for mathematical rigor and proofs? Perhaps you hope to inspire visual learners to dig deeper into mathematics, to see that it's not all about numbers and calculating? Then, you might not presume much more than an interest in pictures and some modicum of logic.
Are you working with high school students? College students? Math majors or not? All of these will affect your answer.
Ultimately, I think there is not much mathematical content with which you need to presume familiarity. I disagree with your "high level" assessment of requisite logic: working with hypotheses and conclusions, as well as some understanding of reductio ad absurdum should suffice. Other than that, a working familiarity with plane geometry should be an advantage but not technically a prerequisite.