I finished the whole series in about 2 days so it's really a quick read and the story is compelling enough for me.
I like the Narnia series for its brilliant imagination, C. S. Lewis' "Britishness" and good sense of humor, as well as those nice kids that can also be so mean to each other. It is said that the world building is inconsistence at times but imo it's never meant to be something like middle earth. And I find the whole multi-verse idea especially the use of stellar evolution pretty neat.
Written before the concept of PC, some minor aspects of it can be a little dated today like some musings about the "good old days", but IMHO it's generally not as mean-spirit as those Narnia haters (those from the liberal or atheist side) claimed it to be, probably with the exception of the depiction of Calormen, which might be commonplace in the author's times. Also in my opinion there's a prevalent sense of "growing up is bad" in it but I think it's reasonable for an escapist fantasy for children & the author himself. The Christian allegory does not bother me at all, but I probably have a high tolerance of preaching, though I still find the all-dead (well, except for Susan) finale a little horrifying.
As to characters I like the first 4 Pevensie kids better than other humans and hated how Susan is basically dumped in the end when I finished it. On the other hand, given it's Christian subtext probably C. S. Lewis just felt it necessary to dump someone to demonstrate the importance of belief and Susan just happened to be his least favorite. After reading a few nice Susan fanfic I think "the problem of Susan" is actually a very good thing.