This is a great introduction to nonlinear regression. The best feature of the book is the extensive use of R code to solve practical problems. If you read this book you will be able to apply these methods almost immediately to your own problems. The fact that the book is small is a bonus as one can actually read and finish the book and actually learn some new skills before getting distracted with something else. The chapter on self-starters shows several cool tricks used to get good initial guesses for the values of parameters in the nonlinear model. Readers unfamiliar with this book can see what others have said here.
To learn this material as well as possible I'm working through the book's exercises and wrote up solutions as I went along. For those who might be interested I'm selling my solutions to the problems in PDF format for 20.00 (US dollars) via PayPal (see the link below).
Code For Various Chapters: