Collapsing the solar system into 2 dimensions. Realising this process of weaponsing the laws of physics is happening all over the universe, and that the universe we currently inhabit is a hobbled shadow of what it once was. One of the only surviving humans gets trapped in a solar system where the speed of light has been lowered to below the escape velocity of its parent star. Stephen Baxter levels of despair. I thoroughly enjoyed it despite the terrible writing. It made me feel awful. Those poor, poor people.
Yeah. Most of the writing in that series is shite. But the last book has some of the most harrowing shit in it I have ever read.
Go on... I don't intend to read the series so spoilers are fine.
spoiler
The solar system gets collapsed into 2 dimensions, killing 99.99% of humanity