Delta Phenomenon was written by Welles Wilder, developer of the widely-used RSI (relative strength indicator). It teaches how there are market cycles ("delta cycles") that are based on astrological relationships like full moons. The cycles predict the turning points in any market, and there are cycles of different lengths - 19 years, 4 years, 1 year, 4 months, and 4 day cycles. Sometimes the cycles have a point where they change, called an "inversion". Other than the occurrence of an inversion, the cycles are constant, so you have the ability to extrapolate the cycle far into the future. The Delta Cycles supposedly work in any market, but each individual market has a unique cycle.
This book is explicit in admitting that the Delta cycle is not a complete trading system. It is simply an indicator used to aid in forecasting. The problem with that statement is that the criteria for Delta cycles is very objective and mechanical, which means that it can easily be back-tested to see if there really is an edge. To be fair though, most useful technical analysis techniques are subject to interpretation, and many users of Delta say that the cycles do indeed need a lot of interpreting. There has also been chatter among traders that the Delta cycles work well with other indicators like Fibonacci or Elliot Wave. This makes sense on the surface since Delta predicts the timing of cycles but not the magnitude, and Elliot Wave predicts magnitude but not the timing.
Unfortunately, this book has many of the telltale signs of a scam:
I bought this book around 1994. It was one of the few times where I wasted money on a trading resource. Normally I would have rated this book 2 to 3 stars since cycle analysis is indeed a valid theory, but the hype and cost take away much of the book's credibility.