If you are starting your own architecture firm, you will most definitely need a copy of The Architect's Handbook of Professional Practice. Written by The American Institute of Architects, the book provides every bit of information needed to build and run an architecture firm - from choosing a legal entity, to recruiting and hiring employees, to delivering a project - all neatly organized into a single hardcover volume.
The book focuses on the business aspects of running an architecture firm and leaves the design side out of the equation. It contains all the stuff you didn't learn in architecture school and all the stuff you probably wish you didn't have to worry about. That is the great benefit of the book - everything is neatly laid out and easy to find. If you are an architect and have only one business book on the shelf, The Architect's Handbook of Professional Practice is the one you should choose.
The one thing that is not included in the book is full access to the AIA Contract Documents. There is a section dedicated to samples of the Documents and there are PDFs included on the enclosed CD; however, in order to actually use the AIA Contract Documents, they must be purchased directly through The American Institute of Architects. This ensures that you always have the most current documents with all of the most up-to-date language that will protect you and your clients.