राज की किताब जूलिया से बेहतर है।
I have answered this. But, disapproved.
That would be "Raj's book is better than Julia."
Why doesn't it work with अच्छा like all the other adjectives?
ज्यादा अच्छा might work
अच्छा just means good, better can be described as 'more good' hence 'ज्यादा अच्छा' can substitute बहतर