This book does a good job at explaining the fundamentals of GPS operation. It breaks things down to an understandable level and presents most material well. However, it is not thorough enough to be used to design a software receiver. The book covers Costas loops and DLL's in a very cursory manner. It is also filled with typos and other errors. If your actually attempting to build a software receiver, try some of these books: "Understanding GPS Principles and Applications" by Elliot Kaplan (Ed.), "Global Positioning System: Theory and Applications Volume 1" by B. W. Parkinson and J. J. Spilker (Ed.'s), "Global Positioning System: Signals Measurements and Performance" by P. Misra and Per Enge. These books are far more detailed and are relatively free of errors.