Books on fire (3)
I believe the answer is:
lit
I believe this clue is a double definition.
'books' is the first definition.
(abbreviation for literature)
'on fire' is the second definition.
(I've seen this in another clue)
(Other definitions for lit that I've seen before include "Fired" , "Ignited, say cigarette" , "Set afire" , "fine writing in condensed form" , "Set alight" .)