One for the books is a phrase used to describe an event or experience that is remarkable, unforgettable, or extraordinary. Antonyms for this expression would include dull, boring, unremarkable, forgettable, ordinary, or mundane. Instead of being an event worth remembering, these experiences are uneventful and may be easily forgotten. A moment that is not one for the books may be considered to be commonplace, routine, or unmemorable. This antonymic expression can be used to describe a variety of activities, from ordinary daily routines to lackluster events and unremarkable moments that lack excitement or interest.