Something entertaining that's repeated in books (3,5)
I believe the answer is:
aga sagas
'something entertaining' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'repeated in books' is the wordplay.
'repeated' indicates the doubling of some letters.
'in books' becomes 'agas' (I can't explain this - if you can you should believe this answer much more).
'agas' doubled is 'AGA-SAGAS'.
'that's' is the link.
Can you help me to learn more?
(Other definitions for aga sagas that I've seen before include "Middle-class semi-rural novels" , "middle-class tales?" , "popular British novels" .)