Here is the basic story... (and yes, it involves vampires, forbidden love and high school)
Bella has resigned herself to her dad's town, Forks. It's not what she wanted but it's for the best. She doesn't expect much of the town or the people. She anticipates school to be a nightmare in a town where all the kids have known each other since they were in diapers. But Bella has always considered herself as somewhat different from the mainstream crowd - a loner, fiercely independent. She just needs to take control of her first day and not let the otherness of it control her. Her counter efforts of small town hostility seem wasted though when people seem to be genuinely nice to her. In an odd inversion of improbability, she is actually popular - ironically not what she wants at all and then... in the crowded cafeteria her eyes strayed to the Cullen family. All beautifully sculpted, aloof, oddly silent...statuesque...then he caught her eye, quickly, fleetingly, menacingly... Edward Cullen.
Bella is taken by his mere presence the moment she sees him across the cafeteria. Just her luck that he scowls when she looks at him; his frustration at her presence is frightening. It doesn't help that she has to sit next to him in Biology, when he angles his chair so far away from her, fists clenched in rage.
To make her week worse, he saves her life and things begin to get hectically involved. Complicated does not describe it.
The two are drawn to each other with an intensity that leaves sparks on the skin, an undeniable attraction that could be deadly to both of them.
As much as the narrative drives the reader forward - the dangers, the evolving love story - it is the
realism which this fantasy is placed in (The real world constructs of Washington DC, the familiar high school set up, the novelty experience amongst teenagers of having your own car, your own new-found independence within the family household) which makes you imagine the scenes so vividly. Also, it puts you in the driver's seat through the 1st person perspective of Bella. You ask yourself "If I fell in love with a Vampire, what would I do?" Another issue raised is the humorous way Bella expresses her insecurities, causing the reader to identify with her immediately.
I've read a lot of fantasy books and watched many a Buffy the Vampire Slayer but Twilight is different. It is beautiful. The words construct a poetry of motion. The intensity between Edward and Bella is palpable. I had butterflies in my stomach. Butterflies very similar to the kind whenever I think of Mr Darcy.