The most common and most likely answer to this crossword clue is the 3 plus 5 plus 3 plus 2 plus 4 plus 4 letter word TWO GIRLS ONE ON EACH KNEE
I've seen this crossword clue in Financial Times
T
W
O
G
I
R
L
S
O
N
E
O
N
E
A
C
H
K
N
E
E
Buddy explains!
The straight part
We know that "book title" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case book title = two girls one on each knee.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.