I always check vacuum. There are two ways, one is a needle gauge which is good but not cylinder specific, and the other is the one i use the most which is a vacuum waveform. With the waveform you get a picture of each cylinders intake stroke, overall vac and it will highlight not only which cylinder has the problem, but often which valve, cyl to cyl blow, low compression due to ring or piston wear, ignition faults etc etc ( with practice of course ! ).
Pico have recently added a vac/pressure transducer to their scope range. I don't know how good it is but I would love to have a go with one. Others on this site have made a similar device from a MAP sensor, like the GM analogue type. The digital Ford type won't do. You can then hook this to your scope and if you reference it correctly with a trigger from No1, you can see each cylinders vac profile across the screen. You will learn a lot about the mechanical integrity of the engine from this simple hookup and it will save you LOADS of diagnostic time.
I can't suggest a book because I learned through experience with this, but if you want I can fax you some pages from my scope manual that may help.