Rick Riordan books in order
61 books in the catalogue, about 589 hours of reading in all; the shortest takes 1 hour and the longest 48 hours.
6 series and 25 standalone books in the catalogue.
Percy Jackson & the Olympians
10 books 1 
The Lightning Thief 7.0 h 2 
The Sea of Monsters 5.2 h 3 
The Titan's Curse 5.9 h 4 
The Battle of the Labyrinth 6.8 h 5 
The Last Olympian 7.0 h 
The Demigod Files 2.9 h 
Percy Jackson's Greek Gods 7.5 h 6 
The Chalice of the Gods 5.2 h 7 
Wrath of the Triple Goddess 5.9 h
The Lightning Thief 7.0 h 2 The Sea of Monsters 5.2 h 3 The Titan's Curse 5.9 h 4 The Battle of the Labyrinth 6.8 h 5 The Last Olympian 7.0 h The Demigod Files 2.9 h Percy Jackson's Greek Gods 7.5 h 6 The Chalice of the Gods 5.2 h 7 Wrath of the Triple Goddess 5.9 h Camp Half-Blood Confidential length not known
The Heroes of Olympus
6 books 1 
The Lost Hero 10.2 h 2 
The Son of Neptune 9.4 h 3 
The Mark of Athena 10.7 h 
The House of Hades 11.0 h 5 
The Blood of Olympus 9.6 h
The Lost Hero 10.2 h 2 The Son of Neptune 9.4 h 3 The Mark of Athena 10.7 h The Demigod Diaries length not known
4 The House of Hades 11.0 h 5 The Blood of Olympus 9.6 h The Trials of Apollo
5 books
The Kane Chronicles
3 books
1 
The Sword of Summer 9.4 h 2 
The Hammer of Thor 8.8 h 
The Ship of the Dead 8.3 h
The Sword of Summer 9.4 h 2 The Hammer of Thor 8.8 h Hotel Valhalla: Guide to the Norse Worlds length not known
3 The Ship of the Dead 8.3 h 4 9 From the Nine Worlds length not known
The Nico di Angelo Adventures
2 books
The Sun and the Star 8.7 h The Court of the Dead length not known
Standalone books
Big Red Tequila 7.1 h 
Demigods & Magicians 3.8 h 
The Lightning Thief (2 editions) 2.4 h 
Rebel Island 6.4 h 
Demigods and Monsters 3.8 h 
The Maze of Bones 4.1 h 
Vespers Rising 4.1 h 
The Demigod Diaries 4.7 h 
The Sea of Monsters The Graphic Novel 2.4 h 
Percy Jackson and the Singer of Apollo 1.4 h 
The Son of Sobek 2.0 h 
The Titan's Curse The Graphic Novel 2.4 h 
The Lost Hero The Graphic Novel 3.5 h 
Percy Jackson's Greek Heroes 9.7 h 
For Magnus Chase: Hotel Valhalla Guide to the Norse Worlds 2.9 h 
Camp Half-Blood Confidential 3.2 h 
9 From the Nine Worlds 3.2 h 
Brooklyn House Magician's Manual 3.4 h 
The Battle of the Labyrinth The Graphic Novel 2.9 h 
The Last Olympian The Graphic Novel 2.4 h 
Camp Jupiter Classified - A Probatio's Journal 2.9 h 
Daughter of the Deep 6.8 h 
The Cursed Carnival and Other Calamities 8.5 h 
The Mark of Athena Graphic Novel 2.9 h 
The Court of the Dead 8.2 h Collected editions
Volumes that gather several of the books above.
The Lost Hero / The Son of Neptune / The Mark of Athena / The House of Hades / The Blood of Olympus 48.4 h 
The Lightning Thief / The Sea of Monsters / The Titan’s Curse 26.3 h 
The Lightning Thief / The Sea of Monsters / The Titan's Curse / The Battle of the Labyrinth 9.2 h 
The Lightning Thief / The Sea of Monsters / The Titan’s Curse / The Battle of the Labyrinth / The Last Olympian 32.9 h 
The Red Pyramid / The Throne of Fire / The Serpent's Shadow 27.0 h 
The Lost Hero / The Son of Neptune / The Mark of Athena 29.5 h 
The Sword of Summer / The Hammer of Thor / The Ship of the Dead 29.0 h 
The Hidden Oracle / The Dark Prophecy / The Burning Maze / The Tyrant's Tomb 27.5 h 
The Lightning Thief / The Lost Hero / The Hidden Oracle 25.5 h 
The Hidden Oracle / The Dark Prophecy / The Burning Maze / The Tyrant’s Tomb / The Tower of Nero 29.3 h The House of Hades Graphic Novel 2.9 h