Discuss the book without it being ruined
The trouble with wanting to talk about a book you're halfway through is that almost everyone who can talk about it has already finished it. Chatter fixes that by putting the limit at your chapter instead of at other people's goodwill.
Reading spoiler-free means being able to discuss a book you are halfway through without anyone mentioning what you haven't read. Chatter solves it by putting the limit at your chapter: the group is at most one ahead and the characters only know what has happened up to where you are, so the limit doesn't rely on anyone's goodwill.
Where you get spoiled, in order of frequency
In reviews, which warn you about the spoiler right after dropping it. In forum threads, where someone answers a chapter-five question with chapter-twenty information. On the back cover, which sometimes gives away things the book takes two hundred pages to reveal.
And in the search box: you type a character's name and the first result tells you how it ends.
How Chatter avoids it
You mark the chapter you're on and that becomes the ceiling for everything in the app. The group is at most one chapter ahead: they can't tell you what they haven't read, because as far as the conversation goes, they haven't read it.
With the characters it's the same and stricter: they only know what has happened up to where you are.
A spoiler isn't only the ending
Knowing that a character makes it to the last chapter alive is a spoiler too. So is knowing there's a twist, even without knowing what it is: from then on you read looking for it instead of reading.
That's why the limit isn't “don't give away the ending”, which is what everyone promises, but not going past your chapter. It's the only version anyone can actually keep.
Frequently asked questions
What if I jump a long way ahead?
You mark the new chapter and the conversation catches up with you. The limit rises when you do.
What if the group is further ahead than me?
It can't be. The group is never more than one chapter ahead of the reader.
Can I discuss a book I've already finished?
Yes. Mark the last chapter and there's nothing left to protect, so everything is on the table.
Does Chatter show me text from the book?
No. Chatter doesn't reproduce the text of any book: it talks about what happens in it, like anyone would.