Book excerpt: When the Unabomber suspect was arrested at a cabin outside Lincoln, Montana, in 1996 no one was more surprised than his neighbor of 25 years, Chris Waits. Now Waits, whom ABC News described as the ''man who knew him best,'' has stepped forward with his significant portrait of Kaczynski. He teamed with veteran Montana newsman Dave Shors to write a riveting story about the secret years in Lincoln. Waits was the only person who could tell this story, which includes a compelling mix of personal observations. Waits shares copies of Kaczynski documents and personal journals obtained from the FBI, most of which have never been published before.