Most executives tend to think about outsourcing only in binary terms: Either we outsource a function (accounting, marketing, R&D) or we don't. But as more functions are outsourced, managing a portfolio of providers becomes more difficult. The authors, both research vice presidents at Gartner Inc., propose a solution—"multisourcing"—which they define as "the disciplined provisioning and blending of business and IT services from the optimal set of internal and external providers in the pursuit of business goals." They spend the rest of their time explaining what to do and how to do it. Note: This book deals solely with handling service providers. Manufacturing outsourcing, they say, creates its own unique set of issues.