"Greasemonkey Hacks" is an excellent introduction to implementing user scripts into your Firefox browser. The book starts by telling you where to get Greasemonkey and how to install it into Firefox. This is then followed by a section on security issues relating to running of user scripts in your browser. It doesn't go into much detail on how to code user scripts (that's not its purpose) but instead it presents you with a large variety of user scripts that you can easily install into your browser once you have Greasemonkey installed.
All of the scripts presented provide a useful resource on how to achieve given effects for when you want to write your own user scripts. Of course retyping the scripts from the book is not the most effective way to get them into your computer particularly with those scripts that are several pages long and the author didn't include information in the book to let you know that there is somewhere to go to download them although it is not that hard to find the download once you realise that there ought to be one. Once you have found and downloaded the zip file that contains all of the scripts it is easy to find the one that matches what you are looking at in the book and the book contains excellent instructions on how to test that you have installed it correctly.