What is the Purpose of the 12 Steps?

In order to assess the effectiveness of the 12 Steps, we must first assess the purpose of the Program of Recovery as described in the basic text, Alcoholics Anonymous.

'Well, that’s exactly what this book is about.  Its main object is to enable you to find a Power greater than yourself which will solve your problem.  That means we have written a book which we believe to be spiritual as well as moral.  And it means, of course, that we are going to talk about God.' - page 45, Alcoholics Anonymous

The problem being referred to in this passage Alcoholism.  Therefore, the primary purpose of the 12 Step Program of Alcoholics Anonymous is to enable the reader to find a Power Greater than themselves, otherwise known as God.  The secondary pupose is to enable the reader to be relieved of alcoholism.