What about audio books, magazines, news, websites, studies?

Reading is so much more than curated dead trees.

I'd count an audiobook as a book. I'd count something published online in the vague shape of a book as a book (e.g. if you read a story or a book-style non-fiction work published electronically). I would not count "news", though, for instance.

Whether you read on a paper book or on an e-reader, a full book is much deeper than just a magazine or news article.