Yes it is right to debate, on books, on customs, on practices, on anything and everything pertaining to religion and ones beliefs. This I say because debate is a form of understanding which humans acquire by gathering different perspectives and their causes from different people. Anything which feels that it is above debate rots soon.
The books when they came into existence and when added upon through the ages have been reflecting the needs of that particular era and age. Clearly to impose or imply those same values and principles today is not practical and rational. No doubt we see a rise in people shunning these institutions.
As far as needing to amend the books themselves, the topic is controversial and shall be opposed tooth and nail by the believers, but definitely they should be at least open to the idea of reinterpretations of the same verses and text and see how their moral, and principles are applicable in today’s modern world instead of sticking to the age old interpretations.
In Hindus earlier debate was a legal form of developing upon the religious scriptures as the base and coming up with relevant meanings. the process is known as “Shastraarth”, wherein learned people having different views and perceptions used to debate on a scripture/topic and their points of view recorded. the speakers had to substantiate their claims and interpretations again through referrals to moral practices and other scriptures. In the end the person who could prevail and prove his point conclusively was not only declared a winner but his views were incorporated with the scriptures themselves for referral purposes. This helped in keeping the original scriptures and their sayings intact and also furnishing different interpretations thereof for people to learn and benefit form.
My personal view is that any religion which is not open enough to accommodate the views and perceptions of its followers, stagnates and dies.