I tried really hard to think of a non - romance series and only managed to think of two.
Lord of the Rings - JRR Tolkien
The Chronicles of Narnia - C.S. Lewis
Never read Harry Potter because my kids drove me crazy watching the movies at least once a day.
I narrowed it down to the top 4 for romance.
Outlander - Diana Gabaldon
Dark Hunter Series - Sherrilynn Kenyon
Dark Series - Christine Feehan
Dark Sword Series - Donna Grant