How to form questions with causative 'make'?

Take a sentence like "The mom made her son read a book."

How would you form a question whose answer is "her son"?

Is this correct?
"Whom did the mom make read a book?"

It sounds odd to me, probably because of that "whom" at the beginning… but maybe is the way to say it. Would "who" be also be correct in this case? And is there any other way you would frame this question that sounds more natural to you?