Something enthralling is fascinating — you become completely absorbed in it. An enthralling book is hard to put down, even when it's past your bedtime.
When things captivate or grip you, they're enthralling. You can find another person enthralling, or a well-made movie, a wonderful concert, or an entrancing painting in a museum. Enthralling comes from the verb enthrall, which means "capture one's attention," but had the original meaning of "enslave." The word comes from the prefix en-, "make or put in," and thrall, from the Old English þræl, "serf or slave."