Colleen Hoover's books are a whole conversation starter themselves, aren't they? I went looking for the parent guide for 'It Ends With Us' because my teen wanted to read it, and I'd heard the buzz. I found a few detailed breakdowns online, like on Common Sense Media and some book blogger sites. They're pretty comprehensive, listing the big ones: domestic violence (both physical and emotional), explicit sexual content, strong language, and substance abuse. They usually note the cyclical nature of the abuse depicted, which is a crucial story element.
What I appreciated was that some guides went beyond just listing triggers. They discussed the context—how the story handles the complexity of leaving an abusive relationship, the protagonist's internal conflict, and the generational trauma angle. This helped me decide it was a 'read-together' book for my situation, not a hard no. The guides often missed nuance on the emotional manipulation, though, which is arguably the heaviest part. You almost need to have read it yourself to really gauge if your kid is ready for that particular emotional intensity, beyond just the checklist of topics.
Ended up reading it first, and yeah, the guides were right on the content, but the emotional weight is something you can't fully summarize in a bullet list.