A Gathering Of Shadows by V. E. Schwab
In this fantasy sequel, the story continues to follow the adventures of Kell, an Antari magician who can travel between parallel Londons, and Lila Bard, a daring thief who has seized a chance to escape her grey life for a more colorful one. As Red London prepares for the Element Games—an extravagant international competition of magic—a dark force is growing, threatening to engulf all the Londons in darkness. Meanwhile, Lila and Kell must navigate their evolving relationship and the dangers that come with it, as they grapple with their identities and the consequences of their actions in a world where peril and magic intertwine.