Havening Technique was developed by Dr. Ronald Ruden, and based on my knowledge the concept was first introduced to Dr. Ronald Ruden by Paul Mckenna when Paul shared Emotional Freedom Technique. It seem a big impact on the development of the Havening Techniques had his twin brother, Dr. Steven Ruden.
You can read Dr. Ronald Ruden books which are:
When the past is always present - This a very good book I would recommend to anyone who would like a bit more in depth understandig related to issues that Havening technique solves.
The Craving brain - I haven't read this book, but because it seems it doesn't mention Havening it might be a bit of out of date, which is my impression after reading some amazon reviews.
You can read more about Dr. Ruden here.