what tense is the feminine mystique written in? first , third or omniscient?
Those are not tenses. Tenses apply to verbs. You are asking about the "person" of the narrative. "Omniscient" is a type of third person narrative.
See
http://en.wikipedia.org/wiki/Third-person_omniscient_narrative
for clarification.
Are you referring to the book by Betty Friedan?
That book seems to have a mix of narrative styles. The first person "I" appears often, but at times she makes omniscient statements of fact and her own opinions.