Test Planning books
See the main testplan page here.
Best Practices for the Formal Software Testing Process: A Menu of Testing Tasks
Critical Testing Processes: Plan, Prepare, Perform, Perfect
Enterprise Integration Patterns
Junit in Action
Managing the Testing Process
Software Inspection
Software Test Automation
The Complete Guide to Software Testing
Why not visit our German sister site software qualität carries our extensive list of Test Planning books. Shortly German language versions and translations will be added.