Say you have this Book on New testiment Studies that you would like him to review and then Send him Richard Carrier's Book: "On the Historicity of Jesus - Why we might have reason for doubt"

Why not send him, "god is not great" by Christopher Hitchens. As a retired ordained pastor I was able to understand the examples which some people without religious training would not know. You can read his book if he wants to read yours and then you both can discuss.

Do nothing, it is better to ignore the inference than to create dissent. He is only doing [ what to him ] is helpful............ Each to his own.....

No just act like it never happened.

I would retirn the book to him....in its original wrappings...as is done when the addressee moved out.

If he is being passive aggressive by sending you this gift, I think you should send it back.

If you openly talk to him about religion and atheism send it back with a funny and sarcastic comment.

You could just ask him why he sent you the book

Skepticism often breaks, or keeps us from using worn out customs. I would read the book and then ask him to explain his choices, especially if it's a self help for skeptics. Granted, I don't know you or your brother, and so am using my own familial behavior patterns as my guide to advice.

What do you mean you're "not a skeptic"? Do you believe any and every thing you see, hear, and read? Everyone is a skeptic on some claims, some people abandon their skepticism to find some justification for religious or other non-evidential claims. Even a religious person is skeptical about most other religions.I

Maybe it's an apologetics book, and you know better than to fall for it? I think you need to better define what you mean...

I’d say be skeptical about it and forward it to a skeptic.

It sounds like he is trying to reach out to you. Has anyone ever died from reading something?

It sounds like he is skeptical of your skepticism. Maybe you could read it and make notes and highlights on the false ideas in the book and return it to him.

I would return it with a note thanking him for thinking of you but you have no interest in the book or reading it.

My antagonistic side says to return it with the note.
You're the only one who can decide which way to go with this one.

I'd call him and tell him that he should send the book to a real skeptic.