Standard PCB Layout Book
One book that helped me quite a lot was Johnson and Grahams "High Speed Digital Design". Quite old, but the theory hasn't changed so still very useful reading.
Analog Devices technical documentation has a few good app notes like "A practical guide to PCB layout" and "PCB Design Issues" 
Their web archives contain some good stuff too.  

Although the theory stays the same, the important factors vary from application to application - e.g. a digital only board, mixed signal (e.g. opamps/ADCs with uC) or analog only board. Grounding with mixed signal can get quite interesting, needing careful attention to return paths, placement of power sources, breaks in plane causing return path to deviate, etc. A high impedance analog signal may need routing well away from anything digital, sometimes even a 90 degree crossing might not be acceptable.
In amplification systems (e.g audio, especially microphone amplifiers) one problem is the (often huge) difference of signal levels and impedances from input to output, so needs careful routing to avoid coupling from output back to input.