What books to read and why to formulate your own method

My challenge is to create a planning and tracking system for an agency with many customers and projects in varying states, on-going support and maintenance issues, and fixed deadlines. Here are some observations:

1. Dates are fixed, but projects appear to be 1-3 months behind
2. Different types of work are not timeboxed - there are no boundary conditions on work activities to create focus
3. As a small company, people have to wear many hats, but some hats work better than others. This has meant that planning has taken a back seat to selling and doing, which makes sense in this environment.

In creating a system, I've suggested reading:

Agile Project Management With Scrum - some of the ideas don't really carry in the fixed-date scenario, but this book does a great job of showing the effectiveness of boundary conditions, the requirement for creativity and improvisation in real life (there is no silver bullet), and the value of empiricism: observe what is happening and make new decisions based on this reality.


Agile Estimating and Planning - the most useful hands-on guide

Extreme Programming Explained - embrace change and set yourself up to successfully live with and manage change