This might be a controversial opinion but I really like how different the tone in Solitaire is from the rest of the Oseman-verse.

Yes, it's edgy teen. But that fits perfectly with the vibe of a depressed teenager who doesn't like socialising and is extremely worried about her little brother.

Both the lightness of Heartstopper and the nihilism of Solitaire are part of a teenage experience and having this balance is great.

The plot is a little hiperbolic and dramatic but tbh, that's exactly how I saw the world at 16.