Well, I'm new to the series in that, I just read them last month.
I saw Twilight on DVD last March and it didn't do much for me. Maybe I was in a bad mood? Then I had a week off and my BFF suggested I read the book. So I did and within a week I read the entire Saga and saw both movies.
The first time I watched the movie, I wasn't really into it, I think because the vampire's didn't seem vampire-y enough for me. Let me state that I am 26 and have been VERY interested in vampires for YEARS now. None of the vampires or legends were anything like sparkly, diamondy vampires and I had a hard time adapting to that. What I did really like about it was that Stephanie had very much the same idea about vampires that I do... I think stakes and crosses and holy water are just plain silly. If you read vampire mythology from around the globe... you'll find little to no basis for those beliefs, either.
Reading the books got me HOOKED. Of course, the book goes far more in-depth than the movie does and it made me understand the movie much better. Without reading the book, the movie appears choppy and empty in spots. The other thing was that living inside Bella's head was almost like living in my own head. I found myself making the same commentary as she did while I was reading. I'm sure this is very typical of most females.
I loved the introduction to Bella and Edward's love story in Twilight and as much as I cried... New Moon was terrific. Eclipse provided even more tears than New Moon for me... and while I did like it... Breaking Dawn was a huge disappointment for me. Overall I love the series, although I was a little put-off by it being a YA book.