The Ion is in many ways a perfect introduction to Plato's style. It has all the elements of the best of Plato - humor, cross-examination (elenchus), Socratic irony, and even a myth - all at a very manageable length.
In Ion Socrates discusses with the titular character, a professional rhapsode who also lectures on Homer, the question of whether the rhapsode, a performer of poetry, gives his performance on account of his skill and knowledge or by virtue of divine possession.