Book freak is as absorbed in punctuation marks? (10)
I believe the answer is:
colossians
'book' is the definition.
(I know that Colossians is a Epistle)
'freak is as absorbed in punctuation marks?' is the wordplay.
'freak' indicates an anagram (I've seen this in other clues).
'absorbed in' means one lot of letters goes inside another.
'punctuation marks?' becomes 'colons' (I've seen this in another clue).
'is'+'as'='isas'
'isas' with letters rearranged gives 'ssia'.
'ssia' put into 'colons' is 'COLOSSIANS'.
(Other definitions for colossians that I've seen before include "As recipients of letter" , "New Testament book" .)