vain, nugatory, otiose, idle, empty, hollow mean being without worth or significance. vain implies either absolute or relative absence of value.
vain promises nugatory suggests triviality or insignificance.
a monarch with nugatory powers otiose suggests that something serves no purpose and is either an encumbrance or a superfluity.
a film without a single otiose scene idle suggests being incapable of worthwhile use or effect.
idle speculations empty and hollow suggest a deceiving lack of real substance or soundness or genuineness.
an empty attempt at reconciliation
a hollow victory
Did You Know?
Otiose was first used in English in the late-18th century to describe things producing no useful result. By mid-19th century, it was being used in keeping with its Latin source otiosus, meaning "at leisure." There is also the noun form otiosity, which predates otiose by approximately three centuries. That noun is rarely found in writing today, but it makes an appearance on the occasional spelling bee word list.
Examples of otiose in a Sentence
since you haven't read the book, I suppose that it would be otiose to inquire what you thought of it