As can be deduced from the title, this book isn't really a beginners' guide (it probably would be called "Learning Vim" if this were the case) but instead focuses on people who have a working knowledge of Vim but want to know more. So don't expect a rehash of vimtutor.
There is quite a lot in there that I didn't know or simply didn't realize about Vim. Basically that just about everything can be customised. From the generation of the status line to just how much auto-completion support is in there.
The book starts with helping you personalize your experience with aspects like the look and feel of the editing area by working with colour schemes and the highlighting system as well as how tabs look like and how to extend GVim with additional menus and buttons for frequently used actions.
Over the course of four chapters the author describes more and more complicated customisations to improve your way to get around files and projects up to setting up an automated coding style. And is some really amazing stuff in here like how to customise autocompletion but also quite a few things that I probably won't ever user (i.e. low-level session handling for views). All these techniques are presented in a recipe-like format.
During these chapters the author most of the time implements those customisations using small to mid-length functions which shows you that just about everything can somehow be controlled using the scripting engine of Vim. The scripting language itself and some addons to it (like the option to also code in languages like Perl and Python) are described in chapters 6 and 7. These offer a nice introduction and also show you methods to distribute your own plugins.
I'm personally not really sure about the structure and the amount of chapters customising received compared to the actual developer tools. But, I guess, that's why this book has the word "Hacking" in its title and not "Programming" ;-)
At least with the eBook version there was also a bit of weirdness with regards to the chapters about vimdiff which was for some reason placed within the chapter about folding. So, yes, the book also introduces vimdiff, which is something I only recently stumbled upon quite by accident :D
Don't reinvent the wheel
That said, the book in just about every chapters refers to already existing scripts provided by community members that improve on functionality introduced there. I was delighted to even find a short tutorial for snipMate, one of my favorite plugins.
A suggestion for the next edition of the book: The MRU extension. It offers a TextMate-like window for jumping between your most recently used files.
GVim is not everything
But plugins are not the only diverse part of the Vim-ecosystem. It's also the
platform it runs on and the frontend it runs in. Sadly the author focuses
nearly exclusively on GVim for graphical frontends and ignores OSX as platform
altogether :-( So is
has("gui_running") not really a reliable way to detect
GVim since it also matches MacVim which doesn't offer the same features as the
Concluding, if you want an introduction into what is possible with Vim beyond what vimtutor has to offer, this is something for you. Hacking Vim 7.2 offers some great tips on how to customise your experience and also introduces you to its scripting engine in order to publish your own extensions.
The book is kind of a combination of recipe-like tips and tutorials which works rather well, although some more depth with some of the chapters would have been nice, considering that the language extensions for Perl, Ruby and Python got whole chapters, each.
If you're interested in working with Vim, I'd definitely suggest that you take a look at the sample chapter.