Jacob has a small but very significant part in Twilight (see Jacob’s "Character Analysis" in Twilight). He basically serves as a tool, or a device to introduce Bella (and the reader) to the Quileute legends of vampires and werewolves. He also explains the ancient peace treaty between Jacob’s grandfather and Carlisle, which stated that the Cullens wouldn’t eat humans and that the two "families" would stay off each other’s turf.
From the first time Bella meets Jacob, though, she likes to be around him, even if he is two years younger than her. She even flirts with him a bit (bad, bad manipulative Bella) to get the dirt on Edward. It works because it’s obvious that Jacob has a crush on her.
In New Moon, Jacob develops into a major character and a potential love interest. Stephenie Meyer was surprised by Jacob’s development herself:
Jacob was my first experience with a character taking over – a minor character developing such roundness and life that I couldn't keep him locked inside a tiny role […] I liked him […] Bella liked him. Her instinctive trust and affection came without my intervention. (source)
No doubt Bella really likes him. She calls him "her personal sun" (8.194), her "gift from the gods" (5.151), her "drug" (9.222). Jacob also becomes the "rock" that saves Bella from drowning. The image of Jacob as a rock as well the name "Jacob" might also be Biblical allusions. If you're interested in that angle, be sure to check out "Symbolism, Imagery, Allegory."
Bella and Jacob meet again in New Moon because Bella needs a good mechanic to fix two dilapidated motorcycles. She’s surprised to find that Jacob has grown into a handsome young man. Hello-oh…
Jacob is surprised as well, and from his enthusiasm and eagerness to please Bella, we can tell the guy still has a crush on her. Even when Bella tells him that she really likes him, but that she will never be able to love him the way he deserves, he says, "That’s my problem, isn’t it?" (9.162). He still seems to hope that, one day, Bella will change her mind. He says, "I’ve got loads of time" (9.150).
Time runs out much more quickly than both of them expected. Jacob turns into a werewolf and, soon after, Edward returns (rather, is brought back by Bella).
After Jacob’s been avoiding Bella for weeks, she confronts him at his house, and is shocked about the drastic change in him. He’s undergone a huge growth spurt, and his body and face are "hardened" and "thicker" (11.114). The biggest change she notes, though, is in his expression: bitterness and resentment. His open, friendly smile is gone. Her personal sun has "imploded" (11.115).
Jacob isn’t happy about his change, either. He finds his involuntary transformation into a werewolf as horrifying, and explains to Bella that the hardest part is, "feeling… out of control… Feeling like I can’t be sure of myself – like maybe you shouldn’t be around me… nobody should" (15.30). (Sounds a bit like Edward's feelings during Twilight, huh?)
Still, Jacob accepts his mission to protect humans from vampires, which causes trouble between him and Bella. Until the end, though, his love and dedication for Bella otherwise remains strong and he keeps to his promise to always be there for her. Once Bella has accepted his half-humanness (which, in turn, helps Jacob accept it), their relationship seems to grow even stronger. Their romantic potential culminates in the moment right after Jacob tells Bella that he should leave because she probably wouldn’t like it if he "killed her friend" (18.80), Alice. He’s about to pull Bella into a kiss (Bella is still undecided, but considering), when the phone rings. Bella races to save Edward instead.
The last time Jacob and Bella meet is when he comes to warn her that, if she becomes a vampire, a war between vampires and werewolves would be inevitable. He clearly feels torn between his loyalty to Bella and to his pack, and in the end reaches out to Bella one final time. But Edward pulls Bella away.
What would’ve happened if Jacob hadn’t picked up the phone? Or, even better, what would’ve happened if Edward had never found out about Alice’s false vision of Bella dying? Where would the story have gone? Would Jacob be a better match for Bella than Edward?
Well, at a first glance, Jacob seems to be closer to Bella’s "kind." He’s half-human at least, he warms Bella when she feels cold, and he makes her laugh. (She never seems to laugh much with Edward.) On the other hand, Jacob’s a monster, like Edward, and although his "call" is to protect humans (rather than eat them), werewolves can still lose control and hurt humans. We don’t yet know if werewolves age or not, which could be another deciding factor in Bella’s choice. Consensus on the popular fan site "Twilight Moms" seems to be that, as long as there is Edward, Jacob doesn’t stand a chance. (source.) What do you think, though? Is Jacob better suited for Bella in the long run?
What will happen to Jacob and Bella’s relationship when she becomes a vampire? Will he count her as his enemy, as Bella fears? Questions upon questions come up about Jacob. That might be the reason Stephenie Meyer wrote and posted a story, "Being Jacob Black," which explains what Jacob is all about. You can download it as a PDF in our "Best of the Web" section.