[Keroberos]

It all depends, since the image(s) in question are being use in an analytical work, using them in a descriptive manner should be fair use in the United States. You should not need to contact the author for permission (although it is considered polite).

It all comes down to this, if you decide use an copyrighted image without permission--even if it's fair use where you don't need it--are you willing to deal with a court battle if the rights holder decides to sue? (This does happen even in cases where it is obviously fair use.)

[ADDED THOUGHT] If this is a for profit book, I would defiantly consult a copyright attorney for advice rather then trusting any info I found on the internet--even from the copyright office (you have to be a lawyer to understand all the nuances of that stuff).