Is 'It Ends with Us' by Colleen Hoover Really a Romance?

Colleen Hoovers best-selling book, ‘It Ends with Us’, follows Lily Bloom, the protagonist, as she moves to Boston and meets neurosurgeon, Ryle, who she ends up marrying. However, Lily and Ryle’s marriage is soon put to the test when Atlas- her first true love- makes an appearance, throwing Lily, into what the readers assume will be, a ‘love triangle’.