All this, and more, in one large, rambling novel (3,12)
I believe the answer is:
the silmarillion
'novel' is the definition.
(I've seen this before)
'all this and more in one large rambling' is the wordplay.
'and' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'large' becomes 'l'.
'rambling' indicates anagramming the letters.
'all'+'this'+'more'+'in'+'i'+'l'='allthismoreinil'
'allthismoreinil' anagrammed gives 'THE SILMARILLION'.
(Other definitions for the silmarillion that I've seen before include "Tolkien epic" , "Epic fantasy" , "Novel" .)