Reading perhaps about unknown in books is of no real value (7)
I believe the answer is:
toytown
'is of no real value' is the definition.
I can't judge whether this defines the answer.
'reading perhaps about unknown in books' is the wordplay.
'reading perhaps' becomes 'town' (Reading is a town).
'about' means one lot of letters goes inside another.
'unknown' becomes 'y' (algebra).
'in' is an insertion indicator.
'books' becomes 'OT' (Old Testament).
'y' placed inside 'ot' is 'oyt'.
'town' going around 'oyt' is 'TOYTOWN'.
Can you help me to learn more?
(Another definition for toytown that I've seen is " Larry the Lamb's home".)