From publisher blurb:
Psionics ARE Different!
Back in the days of 1e for groups running of The World's Most Popular Role Playing Game, psionics were A BEAST! Rare and devistating. The only thing protecting non-psionics was that psions could only utilize a small number of attacks against them. (That, and psionic use attracted psionic baddies...) Otherwise, the average fantasy character was virtually helpless.
Here in this psionic tome, the 3e idea of psionic/magic transparency is maintained to provide some parity between psions and non-psions. But to recapture a sense of the older version of the game the tranparency is not 1:1. Magic protections and suppressions only work about half as good versus psionic powers and visa versa. The rules are adjusted this way so that there is at least some way to defend against the psions, but they still can beat the crap out of you after a few bad rolls.