The most common and most likely answer to this crossword clue is the 8 letter word HARDBACK
I've seen this crossword clue in The Sunday Telegraph
H
A
R
D
B
A
C
K
More clues leading to the result HARDBACK
- Demanding second book
- Difficult to support one sort of book.
- Book difficult to endorse
- Journalist has penned awfully drab sort of book
- Book by poet and journalist Spooner’s mentioned
- Book is easy there, but …
- Type of book that’s difficult to finance
- Book hotel and a second on way
- Penguins are rarely so exhausting, as before
- Tough second book
Buddy explains!

The straight part
We know that "book" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case book = hardback.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 HARDBACK mean?
HARDBACK noun- A book with a solid binding.
- (of a book) Having a solid binding.