A magia Nondetection oferece proteção contra todos os feitiços de adivinhação?

Não.

Pergunte ao Kobold: Eu espio com meu pequeno olho por Skip Williams, disse nuff.

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

E se o homem que escreveu o livro está errado, então todas as regras são.

Definitivamente funciona contra o See Invisible. Os feitiços listados aqui são usados principalmente como exemplos, não como uma lista final. A passagem que destaca isso melhor é:

...becomes difficult to detect by divination spells such as clairaudience/clairvoyance...

...If a divination is attempted against the warded creature or item,...

Ênfase minha. A não-detecção protege contra todas as magias de adivinhação.

Parece que o recebedor do feitiço de Não-detecção ganha SR contra magias de Adivinhação que normalmente não estão sujeitas a SR. Tipo de "detecção invisível a mágica", mas não detecção normal.