Here's the list of significant characters that have been consistently mentioned throughout the length of the book. [SO FAR]
Personal Issue [Relevant to this particular character] : Satellite colony in lungs [Also diagnosed with Thyroids and is very depressed.]
Update: Had level IV Thyroid Cancer at age 13.
Attends a "Support Group" made for children with issues like cancer and such, for kids between the ages of 12-18.
Age: Currently unknown
Personal Issue: Currently unknown
Also attend the Support Group and is a friend of Hazel's. They both seem to have some form of hatred for the Support Group, both having a common enemy helped in creating a bond between the two.
Personal Issue: Had cancer in his, how do I put this... balls. Anyway, he was treated and is fine now, but seems to be socially awkward, addicted to video games and was divorced. Leads the Support Group and seems to be super depressed.
Age: 17 [When first mentioned.]
Personal Issue: Had cancer in his legs.
Currently, I have no knowledge of the place or time in which this book is set.
Hopefully more details will arise as I continue to read.
I know of four mentioned characters of significance: Hazel, Patrick, Isaac and Augustus.
What occurs in the second chapter of The Fault in Our Stars
Hazel has just told her life story to the Support Group, and after the support group ends, she goes with Augustus to his house and they do random stuff. Talk about favorite books, watch movies, talk about what their medical issues were, etc.
We learned that Hazel had level IV Thyroid cancer at age 13 and ended up with a lot of fluid in her lungs. She said it was a miracle she survived. We also learned that Augustus has a secondary name which would be "Gus."
No new characters turned up in this chapter.
What occurs in the third chapter of The Fault in Our Stars
Hazel and Augustus have been hanging out more an more together. Hazel and Augustus exchanged books. Hazel gave Gus An Imperial Affliction and Gus gave Hazel Midnight Dawns. Hazel also has her 33rd half birthday and spends the day at the mall. She meets up with one of her old school friend, Kaitlyn and shops with her. Hazel gets even more in Gus' book series and buys the next two books.
Age: Unknown [Most likely the same age as Hazel, both being from the same grade before Hazel was forced to drop out. - 17]
Role in Chapter: Goes shopping with Hazel in the mall on her 33rd half birthday. [Hazel's 33rd half birthday.]
What occurs in the fourth chapter of The Fault in Our Stars
Hazel talks about what happens in "The Imperial Affliction," a book that she really loves. Hazel and Augustus talk more about their exchanged books and how they liked or may not have liked them. Hazel goes to the movies as well. Towards the end of the chapter, Isaac throws a temper tantrum in Augustus' house. Gus tells Isaac to break his basketball trophies because Gus hates basketball now. Isaac shows no signs of mercy. Augustus used to like basketball, but doesn't anymore.
No new characters turned up in this chapter.
What occurs in the fifth chapter of The Fault in Our Stars
Augustus seems to really like the book: An Imperial Affliction, and wants to talk with the author of the book. He responds to Gus' e-mail, but not Hazel's. Isaac also had surgery to try and get rid of his cancer. The operation was successful and that Isaac was cancer-free. Except Isaac is now blind.
Character: Peter Van Houten
Role in book: Peter is the author of Hazel's favorite book, An Imperial Affliction.
What occurs in chapters 6-15.
Augustus and Hazel continue to converse with Peter Van Houten. Hazel gets plenty of fluid in her lungs and is rushed to the hospital. Peter Van Houten invites Hazel and Gus to Amsterdam. They cannot afford the trip, but a foundation that grants wishes for the terminally sick will give one wish to Hazel and Gus. Hazel spent hers at age 13. Gus used his to being Hazel to Amsterdam. When Hazel and Augustus reached Amsterdam and visited Pater Van Houten, it turns out Peter was lying the whole time, and was a a fat, sick drunkard who hates americans. This disappointed Hazel and Gus, but they still enjoyed the other sights in Amsterdam. Upon returning home, blind Isaac, Hazel and Gus egged Isaac's ex-girlfriend, Monica's house and car. Hazel's dad also read An Imperial Affliction by Peter, but Hazel and Gus weren't too fond of Van Houten anymore.
Role in book: Peter Van Houten's very kind assistant. Resigned due to Peter's rudeness to Hazel and Gus.
Age: Unknown [Most likely around Isaac's age.]
Role in book: Isaac girlfriend [UPDATE: Now ex-girlfriend.]
Character Update: Peter Van Houten
Update: Turns out to be a fat, sick drunkard who hates americans. He says rude things to Hazel and Gus.
What occurs in the last chapters.
Hazel and Augustus are back in the US, and Augustus' cancer has returned. His cancer continues to worsen, taking his right leg. Augustus gets sicker and sicker, to where he can no longer walk. Augustus holds a pre-feuneral, predicting when his death would occur. 8 days following his pre-feuneral, Augustus dies. Hazel and Isaac are extremely disappointed. Peter Van Houten shows up to Augustus' funeral attempting to redeem himself. Peter promises he'll have a better attitude and says he'll continue to write books. Hazel looks for a piece of paper the Augustus had written on. After days of searching, she finds it. Hazel responded with an "I do, Augustus."