(Of a book) totally engrossing

• Not at all susceptible to gibes like 16 across, if absorbing

Wiktionary Word definitions in Wiktionary
a. Of a book or other written work, captivating; engrossing.

WordNet Word definitions in WordNet
adj. (of a book etc) so well written and entertaining as to be difficult to put down; "Unless the story is at once as unputdownable to a taxi driver as to a university professor it is not good enough"- Brian Burland

Longman Dictionary of Contemporary English Word definitions in Longman Dictionary of Contemporary English
adjective EXAMPLES FROM OTHER ENTRIES ▪ This book might be an unputdownable expose of London's underworld, but its moral message is highly dubious.