For those Christians who dislike the Left Behind series, one of the key reasons (the biggest for me especially) they dislike them and call them non-Christian is because they are chiliastic.
To many (if not most) orthodox Christians, chiliasm (sometimes called "millenniarianism") was a heresy that was condemned in the Second Ecumenical Council because of its heavy traits in other heresies of the time (Apollinarians especially from what I've heard). It rejects, to me and to those who agree with me, that there is only one Resurrection (which is firmly stated in the Creeds; not many, but ONE), only one Judgment (again, see the Creeds), and, perhaps most importantly of all, only one Second Coming.
Are these books good fiction? I have no doubt that they are to millions of devout readers. However, I find their theology disturbing (and very anti-Catholic [and by association, anti-E/O Orthodox, anti-Lutheran, and anti-Anglican]).