What swordguy, c.t.,girl, destroyer2000, Yojimbo, et al. said.
And,
Perhaps the book represented an aspect of the instructor's understanding of the enlightenment - it was, after all, a time filled with things we would now call obscene, inappropriate, and unfit for public use. While perhaps the instructor should have known better, as you haven't said the title of the book, I'd be inclined to give him the benefit of the doubt. He may also have heard that the book was commonly used in similar classes, and wanted to give you a modern education.
Alternately, if the book was really too objectionable, it might be beneficial to ask someone in the school administration (say, if you have someone you're supposed to go to for advice, ask them what you should do in the situation - I don't know the leanings of your school, but some christian schools have restrictions on the kinds of materials used for teaching. (from your age, it looks like this is junior high?) On the other hand... well, there are always too many other hands.
Oh, and Mave, have I got a
twisted book for you...
It's called "The art of knot-tying and nautical rope-work"