This book, written by John Jamieson, was suggested reading by forum member djinnee for a lot of useful information regarding the old Culdees on this thread: http://culdiantrust.org/culdianforums/index.php?topic=181.0
The book is past copyright and may be read in full by downloading the text attachment djinnee has kindly provided for us that I have attached to this post.
Enjoy, and thanks again djinnee!