The Last Hours is the current Shadowhunter series. It takes place in 1903, and and features Cordelia Carstairs — a Shadowhunter trained since childhood to battle demons. When her father is accused of a terrible crime, she and her brother travel to London in hopes of preventing the family’s ruin. Cordelia’s mother wants to marry her off, but Cordelia is determined to be a hero rather than a bride. Soon Cordelia encounters childhood friends James and Lucie Herondale and is drawn into their world of glittering ballrooms, secret assignations, and supernatural salons, where vampires and warlocks mingle with mermaids and magicians. . .
The Last Hours is a sequel of sorts to The Infernal Devices. It does not spoil any books taking place in the current timeline, like Dark Artifices or Wicked Powers.