I love to devour two book collections as a whole (2,4)
I believe the answer is:
in toto
'as a whole' is the definition.
(synonyms)
'i love to devour two book collections' is the wordplay.
I cannot really see how this works, but
'i' is within the answer.
'love' could be 'o' (love means zero in tennis) and 'o' is present in the answer.
'to' is present in the answer.
'book' could be 'nt' (New Testament) and 'nt' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for in toto that I've seen before include "overall" , "As a whole (Lat.)" , "Tranquillity" , "Altogether, completely" , "As a whole (Latin)" .)