Book Month: nothing surpasses a good book (6)
I believe the answer is:
octavo
'book' is the definition.
(I've seen this before)
'month nothing surpasses a good book' is the wordplay.
I cannot really understand how this works, but
'month' could be 'av' (Av is an example) and 'av' is present in the answer.
'nothing' could be 'o' (O resembles 0) and 'o' is present in the answer.
The remaining letters 'cto' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for octavo that I've seen before include "Common book size" , "An eight-leaved book or page" , "Size of a book, pages are made by folding a sheet of paper three times to form eight leaves (6)" , "Size of book page" .)