My girlfriend Daisy is a big fan of the Twilight films/books after her friend told her about them. She got into it late in the game, but I promised to watch every movie with her as long as she read the book. I never read the books myself, but I was happy to have her reading at least something. She finished all the books in a long marathon last year, so I saw this coming months ahead of time. Even though I like to poke fun of the movies, I don't think it's as bad as some claim, but on the other hand it's not the masterpiece fan-girls rave about.
The movie picks up right after Eclipse with Edward Cullen and Bella Swan getting married. Since they didn't want to let-down fans by cramming one large book into a 2-hour movie, Part 1 is mostly about their martial problems. Which come off like a really bad paranormal-romance reality show.
Things get really awkward when the new Mrs. Cullen finds out that she's carrying a half-vampire baby and nobody knows for sure how it will affect everyone's lives or safety especially Bella's frail human body. So Bella, Edward, the other Cullens, Jacob Black, and the other shape-shifting wolves take different views of what should happen to the new Baby Cullen.
So since the movie ends about (I assume) halfway in the book, there's really no major villain. The big drama is caused when Jacob's wolf friends decide to kill Bella's baby before it's born (against his wishes) knowing that it will result in Bella's death, ironically the very human they previously risked their lives to protect.
Ironically as the movie progressed, it kinda reversed what I liked and hated about the series. I actually begun to the believe in Edward's and Bella's "love" for one another when faced with burden and doubt. Sadly the action parts (I admit that I do really like vampire lore and powers in the series) are a bit lackluster since it lacks real antagonists. It will please most Twilight fans, but I'd bet Part 1 will further corrupt your opinion if the series hadn't hooked you yet. For those who've seen the previous 3, but not Part 1 I'd advise to wait until Part 2 comes out. For as mixed as I feel about the film, the cliffhanger won't feel so harsh if you can go to the movie theater when you get done with the DVD.