Reddit mentions of A Concise Introduction to Ethics

I haven't read What We Owe to Each Other, but from what I'm familiar with it's an attempt by Scanlon to explain and justify his particular brand of moral contractualism, and not an introductory book on ethics and moral philosophy. I believe Chidi is a contractualist and deontologist so it makes sense why he would like that book (as a philosophy professor), but that's just one area of moral philosophy.

One of the problems with philosophy is that the works are intended for students and educated audiences and not laymen, so most of the books for example that I read when I first started college (and books that you'll find listed in "good for beginners" lists) like Nicomachean Ethics and Groundwork of the Metaphysics of Morals I would never, ever recommend to a general audience. They're full of confusing philosophy terminology and long, multi-stage logical arguments.

Instead I highly recommend what I suspect you're really looking for in Justice: What's the Right Thing to Do? by Michael Sandel. While clearly aimed at an American audience, it's a very good and more importantly very readable general introduction to ethics and the varying schools of thought in the field. It's a really short read for a philosophy text and is peppered with real-life examples and dilemmas.

Another book that I actually read recently and quite enjoyed is A Concise Introduction to Ethics by Russ Shafer-Landau. Unfortunately, this one is intended for a student audience and is more of a textbook (complete with end of chapter quizzes), but it goes really broad and over not just all the big schools of ethics but also the fundamentals of moral reasoning, and metaethics and natural law (two things that don't always show up in ethics books which are usually about normative ethics).