Some of the approaches I've seen for project management and development life cycles are relevant only to a particular size of project. Is the material in the HF PMP book geared to a particular-sized project or is it applicable to any size?
The material on the PMP exam is based on the PMI Guide the the Project Management Body of Knowledge, or PMBOK(r) Guide (and a few other standard project management practices, which are mentioned in the PMP exam specification). The PMBOK(r) Guide isn't geared to any one kind of project -- it's meant to be a guide to project management practices for many different types and sizes of projects, and covering many different industries.
But one thing that the PMBOK(r) Guide is clear on is that no project or company uses every practice. It specifically says that you need to select a project methodology based on the team, the size of the project, the deadlines, and the specific industry you're working in. There's no "one-size-fits-all" methodology that's prescribed by the PMBOK(r) Guide. In fact, if you take the PMP exam, it's possible that you might get a question that requires you to know that there's no one set methodology that you use on every project.
Author of Learning Agile, Beautiful Teams, Head First C#, and Head First PMP (O'Reilly)