No discussion of numbers (KPI, Fibonacci, or otherwise) would be complete without this work by E.T. Bell.
This book is on my desk and always calls out and says, "read some more". It is one of those books that belongs in the library for just that day when it is needed. In one of Taleb's books he remarks about the quality of one's library is not the quanitty of books that have been read, but by the collection of books not yet read.