Which is the longest book series?
Terry Pratchett's Discworld
The Chronicles of Narnia
The Chronicles of Narnia
The Chronicles of Narnia
Harry Potter and the Deathly Hallows
The Chronicles of Narnia
Harry Potter and the Deathly Hallows
The Chronicles of Narnia
The Lord of the Rings
Harry Potter and the Goblet of Fire
Harry Potter and the Order of the Phoenix
The Harry Potter and the Deathly Hallows
The X-Files
Harry Potter and the Deathly Hallows
The Twilight Saga
The Lord of the Rings
The Chronicles of Narnia
Harry Potter and the Goblet of Fire
The Chronicles of Narnia.
Harry Potter and the Order of the Phoenix
Buffy the Vampire Slayer
The X-Files
The Harry Potter and the Deathly Hallows
The Dresden Files
The Twilight Saga
Harry Potter and the Deathly Hallows
The Chronicles of Narnia
The Lord of the Rings
Hitchhiker's Guide to the Galaxy
Lord of the Rings
The Chronicles of Narnia.
The Chronicles of Riddick
Harry Potter and the Goblet of Fire
The X-Files
Buffy the Vampire Slayer
Harry Potter and the Order of the Phoenix
The Dresden Files
The Twilight Saga
The Harry Potter and the Deathly Hallows
Harry Potter and the Deathly Hallows
Lord of the Rings
Dungeons & Dragons
The Chronicles of Narnia
Harry Potter and the Deathly Hallows.
The Lord of the Rings
The Chronicles of Narnia.
The X-Files
The Harry Potter and the Order of the Phoenix
The Dresden Files
The Harry Potter and the Goblet of Fire
Buffy the Vampire Slayer
Harry Potter and the Order of the Phoenix
The Twilight Saga
Hitchhiker's Guide to the Galaxy
The Chronicles of Riddick
Lord of the Rings
Harry Potter and the Deathly Hallows series
Harry Potter and the Deathly Hallows
Harry Potter and the Deathly Hallows.
The Lord of the Rings
The Chronicles of Narnia.
The Silmarillion
The X-Files
The Chronicles of Narnia
The Dresden Files
Chronicles of Narnia
The Twilight Saga
The Harry Potter and the Order of the Phoenix
The Harry Potter and the Deathly Hallows
Harry Potter and the Order of the Phoenix
Dungeons & Dragons
Lord of the Rings
Harry Potter and the Deathly Hallows series
The Harry Potter and the Goblet of Fire
The Silmarillion
The Dresden Files
The X-Files
The Chronicles of Narnia.
Harry Potter and the Deathly Hallows
The Chronicles of Narnia
Harry Potter and the Deathly Hallows.
The Lord of the Rings
Harry Potter
Tales of a Wimpy Kid
The Chronicles of Riddick
The Twilight Saga
Harry Potter and the Order of the Phoenix
The Harry Potter and the Philosopher's Stone
Hitchhiker’s Guide to the Galaxy
Lord of the Rings
Dungeons and Dragons
The Silmarillion
The Dresden Files
Harry Potter
The X-Files
Harry Potter and the Deathly Hallows series
The Legend of Korra's Saga
The Chronicles of Narnia
Chronicles of Narnia
Tales of Vesperia
Harry Potter and the Deathly Hallows
Hitchhikers' Guide to the Galaxy
Harry Potter and the Deathly Hallows.
The Twilight Saga
The Lord of the Rings
The Chronicles of Narnia.
The Harry Potter and the Order of the Phoenix
Tales of a Wimpy Kid
Harry Potter
Harry Potter and the Order of the Phoenix
Buffy the Vampire Slayer.
Buffy the Vampire Slayer series
The Harry Potter Chronicles
Lord of the Rings
The Silmarillion
The Dresden Files
The Harry Potter and the Deathly Hallows
The Harry Potter and the Goblet of Fire
The Chronicles of Riddick
The X-Files
The Chronicles of Narnia
Buffy the Vampire Slayer Series
Harry Potter and the Deathly Hallows series
The Twilight Saga
The Chronicles of Narnia.
Harry Potter and the Deathly Hallows
Hitchhiker’s Guide to the Galaxy
The Harry Potter and the Chamber of Secrets
Harry Potter and the Deathly Hallows.
The Legend of Korra's Chronicles
The Chronicles of Narnia series
Tales of Vesperia
Tales of a Geisha
Harry Potter
Warhammer 40,000
Dungeons and Dragons
The Lord of the Rings
The Silmarillion
The Legend of Korra
The Dresden Files
The Sword in the Stone
Twilight Saga
The Legend of Korra's Books
Buffy the Vampire Slayer.
Buffy the Vampire Slayer series
The Harry Potter and the Philosopher's Stone
Hitchhikers Guide to the Galaxy
The X-Files
The Chronicles of Narnia
Chronicles of Narnia
Buffy the Vampire Slayer Series
The Twilight Saga
The Lord of the Rings Series
The Sword and the Sorceress
Harry Potter
The Chronicles of Riddick and Son
The Harry Potter Chronicles
The Sword of Truth and Sorcery
Warhammer 40,000
The Chronicles of Narnia.
The Chronicles of Riddick
Sword and Sorcery
Harry Potter and the Deathly Hallows.
The Sword and the Sorcerer
The Dresden Files
Lord of the Rings
Warhammer Fantasy Roleplaying Game
The Harry Potter and the Order of the Phoenix
Tales of a Wimpy Kid
Twilight Saga
The Harry Potter and the Deathly Hallows
The Harry Potter and the Order of the Stick
Inspector Gadget
The Discworld Saga
The Silmarillion
The Legend of Zelda's Key
Hitchhiker's Guide
The Lord of the Rings
The Legend of Zelda
Dragonlance: The Last Airbender
The X-Files
Hitchhikers Guide to the Galaxy
Dungeons & Dragons series
Harry Potter
Buffy the Vampire Slayer.
Dungeons & Dragons.
The Twilight Saga
Warhammer 40,000: The Last Olympian
Buffy the Vampire Slayer series
Discworld
Sword and Sorceress
The Chronicles of Narnia
Hitchhiker's Guide To The Galaxy
Buffy the Vampire Slayer Series
Buffy the Vampire Slayer Trilogy
The Silence of the Lambs
The Legend of Zorro
Dungeons & Dragons,
The Saga of Jack and Jill
Harry Potter and the Sorcerers' Stone
The Legend of Korra's Saga