This book was the first I bought and I found it very worthwhile reading.
If you have not read any books on the subject, this book is an ideal
starting point.
Please note that I do not make any money on recommendations.
Free Leaflet
This leaflet is from the UK NHS and gives some very good explanations
as to the thought process of someone suffering from social anxiety.
The leaflet also contains an introduction of the beginning processes
a person suffering from social anxiety can use to start to overcome
social anxiety.