Who would have known back in 1993 that HarperCollins's respectable 25,000-copy launch of Men Are from Mars, Women Are from Venus by John Gray would accumulate such heavenly bestseller stats? In fact, the author's first appearance on Donahue was preempted by the bombing of the World Trade Center. Now, Gray and his book are celebrating their four-year run on the PW charts. With well over six million copies in print and little sign of a slowdown in sales velocity, Mars/ Venus has, on average, gone back to press every two weeks since its initial publication. Sales for July alone topped 26,000. Gray's tome, according to HC communications manager David Rakoff, has been called "the most successful book of the last decade."