I actually enjoyed the Divergent books, for the most part. That being said, Insurgent was basically In Name Only. And, from the trailers, Allegiant is even further from the book.
That being said, if you want a post-apocalyptic YA series with a strong female lead, I would recommend either Scott Westerfield's Uglies series (Uglies, Pretties, Specials, and Extras), or Jolene Charbonneau's The Testing series (The Testing, Independent Study, and Graduation Day). Both series are far better.