[lassejansen]

I don't think it's useful to extract every guard statement into a separate function. Consider importing a json file where each field could potentially contain invalid or missing data. Sure, you could create functions like parseTitle, parseSubtitle, parseAuthorName etc. but these functions will probably only be called from one place and I don't think they improve readability.

On the other hand, I do think that larger functions should be broken up into smaller parts where it makes sense, e.g. a separate function for parsing each object in the json example.