This is an outstanding book for those who want to learn the theory about ethics.
Rieder goes into the great debates, which he calls a "the puzzle."
He spends most of the book discussing what the puzzle is and what are some proposed ways of solving it.

He spends about 10% of the book digressing into the topic of abortion, even though this book is supposed to be about climate change.

Although he tries to link the two issues, it feels like a distraction or a way to get something off his chest.

If you're hoping to get practical tips on what you should do to minimize climate change, you'll be disappointed.

This book is full of nuance, which is nice, but it feels like a nothing-burger.

He rightly points out that having kids is perhaps the most profound, ethical question we face. Each child has enormous impact. Yet few environmentalists bring up the elephant in the room.

He has one child.

He is mostly a vegan, but not militant.

You can see his perspective from these two data points: his point is we must do our best but not be purists because being a purist is a fool's errand.

This would have been a great article.
For a book, it's a bit too long unless you enjoy learning about how he reached his conclusions.