Yep, Jill's story takes up about a third of the novel. I was confused because I heard she wasn't in the new movie. I watched it last night and she's not.Jill is in the story for Extinction in the novel? Mind explaining? I'm not likely to ever bother reading the novel, unless this is actually interesting.
In the book, one chapter will be about Umbrella's base, the next about Jill who's traveling alone, then Alice who's also traveling alone, then Claire/Carlos/LJ and the convoy. Jill's story continues throughout the whole book. She's meets up with some other survivors in a city, helps them defeat some 'bad dudes' who are hoarding supplies and is then convinced to stay on as a leader...
The books are written from the scripts/screenplays. It's normal for a novel to have more details and information than the film and also common for slight changes to be made during filming or in editing. But I'm not sure what's gone on with the Extinction novel vs film.
The film has no scenes or even mentions of Jill at all. It was either written from an early script which was later changed or the author decided to add the Jill story to pad out the book or please fans. Perhaps they decided to scrap the Jill story because of time or budget constraints or maybe they couldn't get the sexy Sienna Guillory back... Her story is quite good and it would have been a better film with it included.
I thought the movie was okay, even though It's got bugger all to do with Resident Evil anymore. Claire (looked nothing like her) and Wesker both sucked (since when was Claire a hard ass, military style 'leader'?). The setting, with the world being consumed by the T-virus would make a good game. Running around a half buried Las Vegas, GTA style would be fun.
If you're interested it's worth a read. The book is cheap... I read a lot at work when I've got night shifts, so I'm always looking for things to read (so my employers paid me to read it ).