I am the sort of person who likes to have a book that tells him more than he can ever possibly know, then when I need to look something up in more detail I know where to go.
This is an in depth but readable guide to the nervous system for anatomists, psychologists, medics, anyone else who needs to know whats inside that blob of jelly in our heads.
If you want a gentle break into the subject try Crossman and Neary, but I promise you that you'll come back to Barr later anyway.
Good regional and functional mix.