E OLDE CURIOSITY SHOPPEEvery man a RembrandtPerhaps there are some mysteries we are not meant to understand. For this category, I nominate the reasoning behind Fed interest rates, everything about Celine Dion and the half-life of fads. Of course, we're herd animals. This is the nation that went ga-ga over the hula hoop, the phrase "You go, girl," and even, God help us, macramÅ½. But does that explain the story told in Paint by Number: The How-To Craze That Swept the Nation?New prosperity and more free time in the 1950s helped fuel a number of trends. But filling in numbered segments to produce a stiff-looking oil painting? No one could have predicted the success of Dan Robbins' invention. Would-be artists went wild, and by 1954, more "number" paintings hung in American homes than did original works of art. As Paint by Number proves, it's not as if the end result for all that hard work turned out to be truly impressive. The Last Supper, for example, looks like a Hari Krishna board meeting; a pensive Jesus could just as easily be Cat Stevens. In the odd cultural history that is Paint by Number, William L. Bird Jr. proves an insightful guide. He explores the relationship between "low" and "high" culture, the increasing influence of the media and the genuine artistic urge satisfied by handicrafts. What cultural historians do is place such pop phenomena in perspective for the rest of us, and in tackling this particular subject, Mr. Bird is a braver man than I am.