Since I've already answered this loads of times, I'm just going to copy and paste it from another question:
First of all, I really dislike the lack of research Stephenie Meyer put into Twilight. It's a sign of a lazy writer, as if she doesn't care. Examples:
- Fail Science: Meyer tried to make her vampires "scientific" by giving them scientific explanations, but they don't make sense, at all. The sparkling, Renesmee, the "eighth colour" Bella sees, all of it is ridiculous. Even though it is "fantasy", it takes place in the real world, not a fantastic one, so it is bound by real world rules. It would have been better if she just explained it by magic.
- Fail Geography: Brazil doesn't have a west coast. Enough said.
- Fail History: She made Rosalie's family rich during the Great Depression because her father was a banker. She made Carlisle tall for someone from his time, and made him hide out in the London sewers before London had any.
- I dislike how whiny Bella is and how she treats her father. Stephenie Meyer says that Bella is mature, but she only shows the opposite.
- I dislike how Stephenie Meyer focused on the relationship instead of a plot. She also gave Edward and Bella too much time in the spotlight, and forgot about finishing other characters' storylines, like Leah's or her friends'.
- I dislike how unorginal the plot is. It's been done many times before.
- I thought it was boring hearing about every little detail in Bella's life. There wasn't enough story.
- I dislike how vain the characters are. Bella only seems to like Edward because he's "beautiful."
- I dislike how Meyer makes humans out to be stupid. Bella only likes to hang out with her supernatural friends, for instance. Everyone else is boring to her.
- The plot holes.
- The really predictable love triangle. I knew Bella was going to end up with Edward, no question. The books made that really clear.
- The love is more like obsessive lust and infatuation.
The messages the books promote:
- That women need men in order to be happy.
- That University is unimportant.
- That it's okay to let your boyfriend control you.
- So much purple prose!
- Words that don't make sense in the context they are used: chagrin, incandescent, scintillating, etc.
- Too many em dashes. A normal book has less than twenty altogether. Twilight has hundreds.
- Awkward sentences. Examples: "I stared without breathing across the long room." "It had been belonged to me since I was born." Many sentences are redundant. They read like, "I opened the door, grasping the handle and pulling it" or " 'What is it?' he asked questioningly". It gets really annoying.
Stephenie Meyer herself:
- She acts really immature, especially regarding Midnight Sun.
- She compares her books and characters to classics and says that her''s are better.
- She doesn't seem to give a damn about her fans.