The most common and most likely answer to this crossword clue is the 6 letter word NOVELS
I've seen this crossword clue in The Daily Telegraph
N
O
V
E
L
S
Buddy explains!

The straight part
We know that "Books" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case books = novels.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does NOVELS mean?
NOVELS noun- A work of prose fiction, longer than a novella.
- A fable; a short tale, especially one of many making up a larger work.
- A novelty; something new.
- A new legal constitution in ancient Rome.