am 18. März 2013
As the author states in the Introduction: “This book aims to do for XNU what Bovet & Cesati's Understanding the Linux Kernel does for Linux, and Russinovich's Windows Internals does for Windows.” Knowing only the latter book, I would say that authors intention have been perfectly fulfilled. For those, which also knows Russinovich's and Solomon's standard work enough said.
For those others: The author understands his matter. He not only describes, but also make understand. To make a picture, the potentially reader should go to [...]. There he can read the Contents of the book and also download a full text of ( very important ) chapter 4. There are also some little tools ( with source code ) for delving deeper into OS X and iOS. Giving the tempo with which operating systems evolve, the book is pretty actual ( Lion ). You have not to read it from page first to page last, but you will be often happy to have it in the bookshelf. And you have not to be an expert in C or Assembler to profit from it ( although having some elementary knowledge of C would enlarge the pleasure ).