Malcolm Harper 
Small Customers, Big Market [PDF ebook] 

This book shows commercial bankers that they can profitably provide microfinance services to the poor. It illustrates, through the experience of particular banks, why banks have become involved and how they have made a success of their involvement.
The eighteen case studies all show that banks can earn good profits at the same time as serving the needs of people who previously lacked access to financial services.
The authors also demonstrate to foreign aid donors, policymakers, NGO staff and microfinance practitioners that it is often quicker, less expensive and more effective for micro-finance services to be provided by commercial banks than by specialist microfinance institutions.