I can't believe the other reviews that this book is not detailed. It contains lots of detail about how the core OS works.
It isn't intended to be an Administrators 'how to' guide, nor is it a programming guide. It is aimed at developers to give them a better understanding of how the OS works and strikes a good balance between being too much of an overview and going into needless detail.
Don't buy this if you want to know such things as 'how do i create user accounts', 'where do I change my networking settings', etc. Get any of the large number of administrator 'companions'
Similarly, don't buy if you are interested in such things as 'which API to use to access accounts in active directory', etc. Again, look at some of the excellent coding books available.
*DO* buy it if you want a really solid understanding of how the OS does its work and are interested in such things as 'what is happening in the background when my system is booting?', 'how does windows map the virtual address space to my physical memory?', etc