Bookends By Bill Eichenberger Columbus Dispatch, 4/25/01 Roger Brucker has spent much of his life in the dark and loving it. The retired advertising executive taught himself "layback climbing in 1933 when I was 4 years old." That first experience ended abruptly when an adult yelled at him never to do that again. "Of course, I paid no attention at all. Each time I explored was more thrilling than the last. Those rocks were mine, my world." Brucker writes of his caving experiences in Beyond Mammoth Cave: A Tale of Obsession in the World's Longest Cave. With his co-author (and caving rival) James D. Borden, Brucker was responsible in part for exploring and thus expanding the known length of Mammoth Cave in Kentucky from 144 miles to nearly 300. Both cavers think the documented length of Mammoth Cave could triple in the not-too-distant future. "If you add in the major unconnected fragments and anticipated lengths of caves under other ridges, you get pretty close to a thousand miles,'' Borden said. Brucker and Borden will discuss and sign copies of Beyond Mammoth Cave at 2 p.m. Saturday at Barnes & Noble, Lennox Town Center, 1739 Olentangy River Rd.