"Percy Jackson and the Olympians" is a book series from Rick Riordan about a boy, Percy, who, after finding out, that he's a demigod, has to save the world from evil titan Cronos. In Camp Halfblood, a camp where demigod get trained by centaur Chiron, he meets Annabeth Chase, who together with his best friend Grover, a satyr, accompanies him through his adventures.
Following up to this series there are another two ("Heros of Olympus" and "Trials of Apollo") where Percy and his new friends need to save the world again, one time from earthgoddess Gaia herself and one time from three overconfident Roman emperors, who want to being the Roman Empire back. Also, they help sungod Apollo, to get back to Olympus, after he was made mortal by his annoyed father Zeus. This three series are partly based on the Greek and Roman mythology.

Inportant characters include:

Percy Jackson (main character, son of Poseidon)

Grover Underwood (Percy's best friend, satyr)

Annabeth Chase (Percy's other friend, daughter of Athena)

Sally Jackson (Percy's Mom, the real goddess here :-))

Chiron (Percy's tutor, centaur)

Luke Castellan (former friend of Percy, now enemy, later Cronos)

Thalia Grace (Percy's cousin, daughter of Zeus)

Nico di Angelo (Percy's other cousin, son of Hades)

Jason Grace (Thalia's little brother, son of Jupiter (Zeus))

Piper McLean(Jason's girlfriend, daughter of Aphrodite)

Leo Valdez (Jason's best friend, son of Hephaestos, able to create fire)

Hazel Levesque (Nico's half-sister, daughter of Pluto (Hades))

Frank Zhang (Hazel's boyfriend, son of Mars (Ares), descendent of Poseidon, can change into animals)

Will Solace (Nico's boyfriend, head healer in CHB, son of Apollo)

Meg McCaffrey (master of mortal Apollo, daughter of Demeter)

Lester Papadopoulos (aka mortal Apollo)

Artemis (Apollo's twin, goddess of moon, hunt and virginity)

And several figures of Greek and Roman mythology and history (mostly parents and/or enemies)

In addition to that there's also a trilogy of books referencing to Nordic/Germanic mythology, "Magnus Chase and the Gods of Asgard". In this books, demigod Magnus Chase and his friends Alex, Sam, Amir, Hearth and Blitzen need to stop Loki from destroying the world.

Important characters:

Magnus Chase (main character, Annabeth's cousin, son of Frey)

Hearthstone (Magnus' streetparent , elf)

Blitzen (Magnus' other streetparent, dwarf)

Samira al Abbas (valkyrie, daughter of Loki)

Alex Fierro (later Magnus' significant other, Sam's half-sibling, genderfluid, child of Loki)

Amir Fadlan (Sam's fiancé, Magnus' friend, normal mortal)

And several figures of Nordic/Germanic mythology as parents and/or enemies.

Also, there is a trilogy referencing to Egyptian mythology, "The Kane Chronicles", where the siblings Carter and Sadie Kane have to save the world.

But I haven't read them yet, so there won't be any ships from that.

So, if you have any suggestions, which Riordanverse-Ships I should rate, please leave them here:

Thank you :-)