What does the cryptic crossword clue "Books of past and series of unremembered days (4)" mean?

The definition is "Books of past". The wordplay uses a hidden word. Hidden in "books of past and series of unrememberED DAys" The answer is EDDA.

Books of past and series of unremembered days (4)

Times Cryptic #28796 | 16 Across | 2023-12-26 flower