Thank you so much. Yes, there will be a second book, and it WILL contain recurring characters! However, I'm not sure which characters as yet.
I'd like to preface this by saying this idea currently only exists as two pages, so anything I say now will be subject to change. However: the next book will feature The City of Frost and Verdigris, a sprawling city suffering under the rule of that tyrant in pink, Princess Roxanne, who is mentioned in Abigail's entry.
Unlike the Goblin Market, it'll be more... defined? As in I'm literally envisaging it as a city-setting that GMs will want to have their players explore, with districts and streets and maybe even maps. Expect to see several members of The Conventicle again: they're hard at work bending powers at work within the city to their mysterious ends. And there's vampires, and mechanical birds. We'll also see Solomon, Melanie, Cassandra and Bear, and the Thing in the Corner for certain.
Beyond that, I'm not sure *yet* but we shall see.