The second book in The Kane Chronicles, so there are spoilers ahead for The Red Pyramid.
It's told in the same format -- as if a transcript from a recording, made by Sadie and Carter in turn, with (small) interjections from their current setting. And instead of merely intimidating that the Egyptian-god-related characters don't go into Manhattan because it's someone else's bailiwick, and mentioning Hermes at a different time, in this one, Carter positively mentions seeing winged horses over Manhattan. I can't remember off-hand whether The Lost Hero had any allusions to The Kane Chronicles, but one can wonder whether they will hook up at some point in the future.
It opens with Sadie, Carter, and Knufu, their baboon friends, on the museum roof ready to steal something along with Jaz and Walt -- who are their students. Apparently their attempts at the end of The Red Pyramid. bore fruit. Unfortunately, the museum closed earlier because a wedding was being staged there.
Some ruckus later, on Sadie's birthday, which she is determined to spend with friends, they learn they recovered one third of the scroll to revive Ra. And Apophis is moving.
Which evolves into another running adventure involving baboons, vultures, a ghost named Mad Claude, a coffin made of water, two love-triangles, a nursing home, a wedding of dwarfs in Tsarist Russia, a boat voyage, and intrigue in the House of Life.
This tale, rather more strongly than The Red Pyramid, leaves threads that point to the sequel, especially between the characters. Still, the adventure ties together well, and resolves well.
(Unlike the Percy Jackson series, this one is not racketting toward more serious. Then, considering it started at the seriousness of The Last Olympian, that's probably well.)