Great background information
From the early days of ESP research, when "telepathy" was a concept, not a popular term, this book documents the author's experiences with mental communication.
For anyone familiar with Sinclair's cynicism, this book is a real jolt. However, if you're familiar with Sinclair's writing style, this book is a delight as well.
The information is compelling, and the story is well-told by someone who, initially, had difficulty believing this himself.
If you're looking for something scientific or modern, this probably isn't the best book for you.
However, if you're interested in the history and development of ESP-related studies, this is a must-read.