Exoplanet Observing For Amateurs. The bad news is that it's out of print (the author, Bruce L. Gary says so himself). The good news is that it's an eBook, and so can be printed on demand! Bruce has been so generous as to provide this awesome resource for Exoplanet enthusiasts.
However, there is one caveat. If you think you aren't ready yet for this book, then do a quick read on Differential Photometry. Apparently, it's the litmus test to know whether you are ready to tackle Amateur Exoplanetology using this book. Go get yourself ready for the planet-hunt!
Bruce L. Gary's Website
eBook (PDF): Exoplanet Observing For Amateurs