For every taste and budget, a paperback

2081: A Hopeful View of the Human Future, by Gerard K. O'Neill. New York: Simon & Schuster. 268 pp. $6.25.

Just when it seemed nobody was willing to write about bright tomorrows, Princeton futurist-physicist O'Neill offers a welcome change of pace. The world of the future, he predicts, will be a place of interplanetary plenty, complete with enclosed cities and passenger service to outlying space colonies.At the same time, O'Neill points out a few sour bites in this pie-in-the-sky future. For instance, he predicts nuclear terrorism will be prevalent in 2081.Most appealing, though, is the author's attachment to reality. O'Neill doesn't traffic on miracle solutions to old problems. All of his predictions are based on existing technologies - and advancements within reach.