Although the authors include hacks for Windows, Mac OS, and even BSD, their expertise and interest are clearly Linux, and later projects use Linux almost exclusively. A fair amount of computer literacy is assumed, and root access is required for most of the software hacks. For example, one hack requires you to make changes to your name server.
The second half of the book mostly covers "hardware hacks". While the authors are clearly much less knowledgeable about the principles of microwave engineering than they are about computer software, they compensate by having a level of enthusiasm that is infectious. (They're not mechanical engineers either; motors are mounted using hot-melt glue, and circuit boards are attached with duct tape). These projects fit well within the definition of a hack: they are quick projects made to solve a problem, without regard for engineering niceties like durability, efficiency, scalability, and appearance. Of course, readers with engineering expertise could always design something better if they needed to.
Wireless hacks have come a long way since the CueCat; while some of these projects would appeal mainly to college students, a few of the projects are highly imaginative, and most of them are (as the kids say) way cool. The biggest downside of the book is that the writing style and English usage deteriorate toward the end of the book, where annoying PCisms begin to slip in. If the authors can fix this flaw, and if they can keep the contents up to date, future editions of this book could become a well-thumbed classic.