You're downvoted but you're not wrong. 'Whom is this book for?' is correct. You can tell because the answer is 'her/him', not 'he/she'. See: http://www.gramma

You're downvoted but you're not wrong. 'Whom is this book for?' is correct. You can tell because the answer is 'her/him', not 'he/she'. See: http://www.grammarbook.com/grammar/whoVwhom.asp http://www.grammarbook.com/grammar/whoVwhom.asp