Beginning WF: Windows Workflow in .NET 4.0 by Mark Collins
Windows Workflow Foundation is a ground-breaking addition to the core of the .NET Framework that allows you to orchestrate human and system interactions as a series of workflows that can be easily mapped, analyzed, adjusted, and implemented. As business problems become more complex, the need for a workflow-based solution has never been more evident. WF provides a simple and consistent way to model and implement complex problems. As a developer, you focus on developing the business logic for individual workflow tasks. The runtime handles the execution of those tasks after they have been composed into a workflow. Beginning WF demonstrates, in an eminently readable and accessible style, how Microsoft's Workflow Foundation (WF) technology can be used in a wide variety of applications.