Definition of "irresistible"

Though his account of written communication over the past 5,000 years necessarily has a powerful forward momentum, his diversions down the fascinating byways of the subject are irresistible ...

2013 September 14, Jane Shilling, “The Golden Thread: the Story of Writing, by Ewan Clayton, review [print edition: Illuminating language]”, in The Daily Telegraph (Review)‎, page R29