I think it depends on what you mean. I don't think that just the number of bytes of data should be used to measure the size of your dataset. For example, if I have 1TB of all 1's, this is a lot of data, but not very interesting.

I think a more nuanced notion of size is the /information content/ of the datasets. I haven't thought about it carefully, but I'm sure you can quantify this more explicitly in terms of information theory or other non-bit-based complexity measures.

From this point of view, literature may not be large (in terms of the number of bytes), but in terms of information content, it is incredibly dense. A large portion of human knowledge is written somewhere. From this point of view, it is in fact big data.