Bulk Book covers kernel basics but missing multi-processor, multi-core handling and virtualization as both host and client which modern Linux kernel has to handle and already handled. Architecture needs many more perspective pictures in both general and in detail instead of trivial words about the implementation details. The other things need to be handled are remoting, x-window, samba, cups, nas and nis from architectural perspective.
However for those who have no idea of implementation details of Linux kernel, it is a great book to go over.
