I am an artist who uses books as my medium. I buy a published book and I add collage, paint, and drawings, and otherwise alter the pages. I don't usually cover all of the text. Does this violate copyright laws, or is it the equivalent of accidentally dropping the book in a mud puddle?

Using existing books as the basis of your collage is likely to be permitted under the law -- but no more than "likely," because the rules are not 100% clear. Here is an explanation of this fuzzy area of copyright law.

If you purchase a book, you are free to resell it, rent it, soak it in mud, or even burn it if you wish (although please be careful with the book burnings). Once the first sale of a particular copy has occurred, the author's rights as to that copy shrink (under Section 109 of the U.S. Copyright Act). But this "first sale doctrine" still doesn't grant you the right to reproduce, adapt, or perform the work. So, the question is whether your collage amounts to an adaptation of the book. If it does, the book's copyright owner could sue you for infringement.

Even the federal courts seem confused about the first sale doctrine. In the past five years, two relevant cases with similar facts arrived at rather opposite results. In one case, a company purchased a book of prints by the painter Patrick Nagel. The company cut out the individual images in the book and framed them for resale. A court of appeals (for the Ninth Circuit in California) decided that this practice was an unpermitted infringement because the company had "adapted" Nagel's work.

In a different case, however, a company purchased note cards and mounted them on tiles. A federal court in Illinois determined that this practice was not an infringement and was permitted under the first sale doctrine. Go figure!

From your description, it sounds like your work is closer to destruction of the book than adaptation, since readers can no longer make sense of the text. Of course, given the uniqueness of your work, there aren't any court cases that present an answer to your question on a silver platter. You may well be legally okay. But you could still get yourself into hot water if you reproduce the collages -- remember, the first sale doctrine doesn't permit reproductions.