Modern Fantasy:
* The Harry Potter series by J.K. Rowling: Arguably the most successful fantasy series of all time, selling hundreds of millions of copies worldwide.
* The Twilight Saga by Stephenie Meyer: This series, aimed at young adults, became a global phenomenon, selling over 150 million copies.
* A Song of Ice and Fire series by George R.R. Martin: While not as commercially successful as Harry Potter, this series has sold tens of millions of copies and spawned the wildly popular HBO series, "Game of Thrones."
* The Hunger Games trilogy by Suzanne Collins: Another young adult success story, with over 100 million copies sold.
* The Wheel of Time series by Robert Jordan: This epic fantasy series, completed after Jordan's death by Brandon Sanderson, has sold over 90 million copies.
* Mistborn series by Brandon Sanderson: A popular series known for its intricate magic system and compelling characters, selling millions of copies.
* The Kingkiller Chronicle by Patrick Rothfuss: While only two books have been released so far, the series has achieved cult status and sold millions of copies.
* The Stormlight Archive by Brandon Sanderson: Sanderson's newest epic fantasy series, already garnering massive popularity and selling millions.
Classic Fantasy:
* The Lord of the Rings by J.R.R. Tolkien: A cornerstone of modern fantasy, selling over 150 million copies worldwide.
* The Chronicles of Narnia by C.S. Lewis: A beloved series for children and adults alike, selling over 100 million copies.
* The Earthsea Cycle by Ursula K. Le Guin: A groundbreaking fantasy series exploring themes of magic, identity, and morality, with over 1 million copies sold.
This is by no means an exhaustive list, but it represents a good starting point for discovering fantasy books that have achieved remarkable commercial success.