Ian Rankin is a lovely man, so kind and patient at events and signings, always happy to answer questions about his characters and writing processes he's probably had million times before.
Neil Gaiman was the same when I met him in the early 2000s, he had a nice thing to say to everyone, and drew a little picture in every book he was given. Also lovely and staggeringly patient was the late, great Terry Pratchett, even though he was clearly knackered from a UK wide tour and the bookshop has seriously underprepared for the arrival of 500 fans of his books.
Most authors are really sweet at signing events, the new, unknown ones are super pleased people have come to meet them, and the more established ones delight in the way their creations are so well loved.