I preordered this book so I have been reading it for about a week now. It is a wonderful book on security research for iOS devices. Don't expect to write a jailbreak for the newest devices after reading this book though, as that would require much experience in writing exploits, fuzzing, kernel debugging and ROP, which is completely understandable. It is foolish to believe that reading one book will allow you to write jailbreaks and find exploits with ease.
The book begins covering sandboxing, code signing and iOS enterprise applications, and their weaknesses. The chapter on fuzzing was very explanatory on the techniques used to do so. It covered fuzzing PDF and powerpoint documents in mobile safari, as well as SMS fuzzing. The next chapter talks about exploitation on iOS devices, focusing on heap exploits and in turn, memory allocation and deallocation.
The chapter on ROP explains what is capable and not capable with return oriented programming, and gives two great examples of such techniques. Following that is a chapter on kernel exploitation, describing how to reverse the IOKit kernel drivers and finding vulnerabilities, as well as how to exploit vulnerabilities once found. This chapter concludes with a demonstration on the heap fang shui technique used for heap buffer overflow exploits.
The jailbreaking chapter is not particularly long, but that is because the techniques used have been described in other parts of the book. This chapter examines the redsn0w jailbreak and describes each step performed by it, including the different kernel patches applied by the jailbreak.
The final chapter covers baseband hacking, which I have not read in detail yet. It appears, at first glance, to cover general knowledge on cell networks leading into the RTOS used on the baseband chips, and ending with a description of the ultrasn0w unlock.
Overall, I would recommend anyone who is interested in the techniques and steps used to find vulnerabilities and exploit them, leading to the development of a jailbreak for an iOS device.