Reading books is a popular hobby as you can easily while away time or just fall asleep reading one. However, it's very easy to get into the habit of buying books you don't end up reading. Interesting enough, there's a term for such a habit: tsundoku. Tsundoku is a Japanese term for people who buy a lot of books they never get around to reading.
The Japanese word doku means "reading", and it comes from tsumu which means "to pile up". So, tsundoku refers to the practice of piling up reading material.
Quite similarly, the term Bibliomania came into the picture when Thomas Frognall Dibdin's wrote a book with the very same title. Bibliomania comes from the Greek biblio, which refers to books, and mania, "madness".
At that time, bibliomania described people who were obsessed with collecting literature, but it now refers to people who collect books on subjects they are passionate about.
Even though these two words have similar meanings, the main difference is that bibliomania focuses on creating a book collection, while tsundoku is about buying books you intend to read that end up gathering dust on the shelf.