In North American usage, skittish has the meaning of fearful or easily scared. It applies to animals, particularly pets that are fearful around children (due to previous rough treatment) and it often applies to single people who are fearful about dating. As Jessie mentioned, skittish investors is another usage. For "not very serious and with ideas and feelings that keep changing," caprious is the standard word (slightly formal, I use it, but I doubt that any of my friends use it) and scatter-brained and flighty are common in spoken English.

I'm a native English speaker from South Africa, and while I don't hear people being described a "skittish", I think it is used rather frequently but mostly with the connotation of being 'nervous' or 'extremely cautious'. Example: She's skittish of driving. Since the economy entered a recession, investors have become very skittish.

I have used the word. I have definitely heard others use it. It is usually used to describe people who are nervous or uncertain about making personal commitments or starting business projects. For example, "He was a bit skittish about coming to the family gathering. He hadn't met any of my family before". Or "She was a bit skittish about investing the money. It seemed a risky venture". Hope this helps

God dag Mikkel! This is a really fun word. Where I'm from (New Zealand), at least, skittish is not in the vernacular at all. Some people may have a sense of what it means, probably from reading books like you have said, but couldn't define it and hardly ever use it regularly. People are more likely to say 'scatty,' or that they have their 'head in the clouds,' for example. Thanks for reminding me of this word though, maybe I should use it and see how people react or understand. All that being said, I'm not sure whether or not it is used in the UK, with its many dialects or the USA. I don't believe it is, but I might be wrong. Maybe someone can correct me there :D In sum, if you are planning to use this word, then by all means try using it, but there is a good chance that people will not understand. I hope this is useful to you or at least interesting.