I have read so far I think eight books in the series. Mostly for the laughs. They are very badly written. They are extremely mis-informed about the Catholic Church, and indeed every non-fundamentalist Protestant faith. Also they really have no idea about the world beyond US shores. The way everybody speaks English and has air conditioning seems especially unrealistic.
Anyway be that as it may, after reading Left Behind I checked out the theology by reading "The Rapture Trap" by Paul Thigpen. I suggest you do the same. It is easy to read and points out quite clearly how Catholic teaching differs from the whole idea of the Rapture which even most protestants do not believe in.
Happy reading.