All right, it might be a *bit* strong to say this book changed my life, but it is undeniably true that it -- and the website associated with it -- have led to some important modifications in the way I work. And that's very close to the same thing.
If you are content with the factory settings your computer was delivered with, it might not be evident to you why this book can have such an impact. But if you like playing around with your technology and adapting it to your own needs and preferences, then you might just get a lot out of it. Part of the reason I think I responded so strongly to this is that my personality aligns pretty closely with the "characteristics of a lifehacker" described in the Introduction: excelling at finding things on the web; "addicted to the 'Ah-HA!' moments in life; eager to go out of their way to avoid tedious or mundane work. Curiosity, efficiency, individuality, technology.
Many of the "hacks" here have to do with fundamental processes like managing email, automating the things you do over and over, or getting your stuff (paper and electronic) in order and making yourself more productive. Some of it is basic, like how to use RSS feeds, but other hacks require a moderate degree of programming ability. Readers who use a computer with any degree of regularity shouldn't be intimidated by this, however. As someone who for years has had to fill out a timesheet as part of my job, the few minutes it took to master Hack 63 ("Quick-Log Your Work Day") have already been repaid over and over again. Gina, where were you in 1996?
Over the last few months, I've read a number of the "Hacks" books from O'Reilly Media -- "Mind Hacks: Tips & Tricks for Using Your Brain (Hacks)," "Mind Performance Hacks: Tips & Tools for Overclocking Your Brain (Hacks)," "Firefox Hacks: Tips & Tools for Next-Generation Web Browsing (Hacks)," and the like. Those are all okay, but none of them were as easy to read, easy to master, or as immediately applicable as "Lifehacker" has been. Maybe not everyone fits the "lifehacker" profile, or would respond to this book with the enthusiasm I obviously have. But I bet most anyone who uses a computer for work or recreation (including buying books online?) would find at least one new way to put technology to work making them less harried, more productive, or just ... happier.