I do a lot of firmware work at my job, but I'm looking for more advanced books on the topic. Things not like the basics of "what is an interrupt". I'm reading the O'Reilly book on embedded systems development which is OK, but not advanced enough. For instance, its rare for books to discuss things like Flash pages (which can be really useful), how to put a section of code in a specific area of memory.
Perhaps something with some tips and tricks. I do primarily PIC programming.