If you mean books to help introverts be less introverted, I can recommend many.
A member of our family suffered social anxiety disorder at a level which was crippling from the preteens to late 20s, when her efforts and natural increases in maturity led to much improvement.
**Dying of Embarrassment: Help for Social Anxiety & Phobia. Markway BG, Carmin CN, Pollard CA, Pollard CA, Flynn T. New Harbinger Publications, Oakland, CA, 1992.
*Painfully Shy: How to Overcome Social Anxiety and Reclaim you Life. Markway BG, St. Martin's Press, New York, 2001.
*The Shyness & Social Anxiety Workbook: Proven Techniques for Overcoming Your Fear. Antony MM, Swinson RP. New Harbinger Publications, Oakland, CA, 2000.
More strongly recommended: SAD responds well to psychological intervention, practice exercises to desensitize her to social interaction, and if necessary, medication which allows her to do those practice exercises. Since the SAD person fears judgment, she is assigned practice interactions with people she is unlikely to care about and/or see again--store clerks, movie ticket sellers, and such. If she cannot perform simple exercises, she may need pharmaceutical help for a short period while she learns how to manage purchases, make small talk, and other normal activities.
Some SAD sufferers eventually gain enough confidence that they overcome it to some degree, although they still tend to be quiet people happy enough with their own company.