It means puzzled and/or confused.

Many authors seem to think it means amused mixed with some confusion or puzzlement or something else like that.

Some dictionaries have started to include definitions along those lines, which is correct to do if that is becoming a common usage. But that makes the word bullshit because it no longer conveys a clear meaning. Unlike some words that gain new meanings through misuse, it's usually not clear which meaning is intended from context. Usually I can easily imagine a character's response to something to be either of these definitions so I often can't understand the author's intention. I often find myself taken out of the story while I try to understand which meaning I should use. Because of this I think the word has become useless and shouldn't be used.