Ask the Kobold: I Spy with My Little Eye by Skip Williams, nuff said.
The nondection spell description could say that it defeats all divination spells (regardless of their descriptors or modes of operation), but it does not. Instead, it specifies a broad subset of divination spells against which it is effective.
So, what divination spells are subject to interference from nondetection? The spell description gives a few clues: nondetection gives some protection against divination spells that are directed against the warded subject or the area the subject is in. In particular:
Divination spells with the scrying descriptor. Clairaudience/clairvoyance is the best example here. If you see the scrying descriptor in the second line of the spell description (right after the spell’s name and school), the divination caster must make a caster level check for the spell to work.
Divination spells with any range entry other than personal or touch. When a divination spell has a range of personal or touch, it grants the spell recipient some extra ability to perceive things and nondetection cannot ward its subject against the spell. When a divination spell has a range other than personal or touch, the spell must be directed at an area or at a specific subject and nondetection is effective against it. It’s worth noting here that scrying spells generally have ranges other than personal or touch.
Here’s a quick (and incomplete) list of divination spells that nondetection does not affect:
arcane sight, greater arcane sight, augury, commune, commune with nature, comprehend languages, contact other plane, divination, find the path, find traps, foresight, guidance, know direction, legend lore, moment of prescience, read magic, see invisibility, speak with animals, speak with plants, stone tell, telepathic bond, tongues, true seeing, true strike, vision
And if the man who wrote the book is wrong, then all the rules are.