Robert James Waller, meet your match. The Celestine Prophecy, the first novel by James Redfield, could be this year's The Bridges of Madison County. Redfield, 43, an Alabama-based therapist, borrowed $20,000 to self-publish his book (about an ancient manuscript that contains nine insights into the human condition) in 1993. Distributed mainly to New Age bookstores, the novel became a cult hit, and major publishers started sniffing around. After a bidding war with Bantam, Warner Books won Prophecy for $800,000 and is shipping the repackaged novel this month. ''It's a reflection of New Age meeting old age,'' says Laurence J. Kirshbaum, president of Warner Books. ''Our only job (in making it a best-seller) is to not screw up.'' The publisher has convinced major booksellers of Prophecy's potential. ''Judging from how the self-published version is doing, they may be right,'' says a spokesman from Waldenbooks. Meanwhile, Redfield is working on a sequel and taking his sudden good fortune in stride. His plans for the future: traveling. ''Money is just a tool,'' says Redfield. ''And you can circulate the planet a little more with it.''