It doesn't mean it's more appealing necessarily, for example, maybe Dickens is borrowed because it's a set text for things (if, for example, I shortly go and borrow Of Mice and Men it's not because I "want" tobut because I need to), or perhaps more people buy Tolkien and borrow Dickens? Also, look at the ratios of number of publications from each author. There are many explanations. Although, maybe Dickens is just more popular among library users, nothing inherently wrong with that IMO.

Sorry, I'll stop being a stats geek for a minute now.