Arcane tomes are not ordinary books that happen to deal with arcane matters. There is intrinsic power in them - a power I've learned to synthesize into a single arcane rune.
Should you find an arcane tome in your travels I will give you one such rune. Only the most powerful wielders of magic carry the books I need. In Outland this usually means Kael's blood elves - but you'd be surprised by where such tomes often turn up.