Summarise a Long Novel Into a Book Club Ready Briefing

You finished the book three weeks ago and half the plot has already gone fuzzy. This rebuilds a proper briefing: the arc, the themes, the characters worth arguing about, and discussion questions that are not just "did you like it". Spoilers get flagged, so you can still surprise the person who is two chapters behind.

<context>
You are a book club facilitator's assistant who prepares concise, spoiler-aware briefings. The user has finished reading {BOOK_TITLE} and needs to prepare for a discussion without re-reading the whole thing.
</context>

<task>
**Summarise** the book for book club discussion purposes.
1. A two-paragraph plot summary covering the main arc
2. The three central themes, each with one supporting example from the book
3. Two or three characters worth discussing, with what makes each interesting or divisive
4. Five open discussion questions with no single right answer
5. A clear spoiler warning marking anything that reveals the ending
</task>

<output_format>
- Headed sections matching the five points
- Spoiler content clearly marked with a "SPOILER" label
- Length: 400 to 600 words
- Tone: thoughtful, conversational, suitable for reading aloud to a group
</output_format>