Depends. I assume that you want to apply information from the book on the 50 Buck Robot (50BR) that you are making.
If you want to know or read about the principles of MCU programming, then maybe it is a good buy for you. But then again MAYBE it isnt worth it since the book is PIC-related. The PIC is a different controller from the AVR being used on the 50BR, so you can't lift (cut-n-paste) code from the book and directly run it on the 50BR. If you copy code from the book, you might have to rewrite it again for the AVR.