Without a summer - Mary Robinette Kowal

Summer, 1816. Glamourists Jane and David Vincent return home to an unseasonably cold Long Parkmeade. Cooped up inside with Jane's fretful sister and father, they soon become restless, so when they receive a commission from a prominent family in London, they decide to go - taking Melody with them. Perhaps the change of scenery will brighten their moods (and Melody's marriage prospects).

The capital is fizzing with talk of crop failures and unemployment riots in the north. Finding it difficult to avoid getting embroiled in the intrigue, it's not long before Jane and David realise they must use their magic to solve a crisis of international proportions . . . and get Melody to the church on time.