It's curious how uneven book has everything (7)
I believe the answer is:
oddball
'it's curious' is the definition.
(thesaurus)
'uneven book has everything' is the wordplay.
'uneven' becomes 'odd' (I've seen this before).
'book' becomes 'b' (abbreviation for book).
'has' says to put letters next to each other.
'everything' becomes 'all' (all things).
'odd'+'b'+'all'='ODDBALL'
'how' acts as a link.
(Other definitions for oddball that I've seen before include "Eccentric 32" , "Bold lad may be eccentric" , "Weirdo" , "Strange, bizarre" , "Weird" .)