Free Yourself from Anxiety: A Self-help Guide to Overcoming Anxiety Disorders by Emma Fletcher and Martha Langley.
This book is for all types of anxiety, and there is a small section about Social Anxiety in it, although I wouldn't disregard it just because it's not solely focused on SA.
I haven't used this book for quite a while now but when I did use it I found it easy to read, and there are some really helpful exercises, tips and relaxation techniques to help with all anxieties.
Amazon sell it and they offer the "look inside" on this book Free Yourself from Anxiety: A Self-help Guide to Overcoming Anxiety Disorders: Amazon.co.uk: Emma Fletcher, Martha Langley: Books
I hope this helps, or if not, I hope you find the right book for you