It's not cheeky to have a high opinion of good books (8)
I believe the answer is:
reverent
'it's not cheeky to have a high opinion' is the definition.
I can't judge whether this defines the answer.
'good books' is the wordplay.
'good' becomes 'revere' (I can't explain this - if you can you should give a lot more credence to this answer).
'books' becomes 'NT' (New Testament).
'revere'+'nt'='REVERENT'
'of' is the link.
Can you help me to learn more?
(Other definitions for reverent that I've seen before include "Deeply respectful" , "Showing devout awe" , "humble" , "Showing holy respect" , "showing much respect" .)