A former student at the library school at UCLA (take a bow, Jenne!) once went on JEOPARDY! (America's Favorite Quiz Show®, no less) and nearly* won by "correctly" providing the question to the answer "The only author ever to have published books in all ten main classes of the Dewey Decimal System." Quite a feat for Isaac Asimov -- if it were true. Sadly, though, it looks like he didn't get around to writing any books that have been classified in the 100s (Philosophy & psychology). Our party-pooping source? This fine list of Frequently Asked Questions. But there's a twist that the Asimov FAQ doesn't mention. There is one record in WorldCat that lists Isaac Asimov as a main personal-name entry and that gives a DDC number in the 100s. But the work in question is a video, not a book. Humanism: Making bigger circles was produced by the American Humanist Association in the 1980s, and features "Dr. Isaac Asimov discuss[ing] humanism in all its aspects -- as a philosophy, as a religion, and its effects on politics." It's classed at 144 Humanism and related systems and doctrines. (Thanks to Thom and Diane at OCLC for help with the WorldCat searches!)
* The buzzer went before she got to write the "v" at the end of "Asimov."