Bartok's embryonic book is a fantasy set in a futuristic society modelled on Victorian England. The High Hats are the ruling class overseeing things, while the Groundlings are human animal hybrids that live in servitude, working in giant factories in an underground zone known as City Beneath The City.
Our hero is Number 13, a shy, foxlike character who has lost an ear in the past and must escape an orphanage to go on a remarkable journey along with best pal Trinket, who is part human and part bird. It won't surprise you to learn that Bartok is planning a trilogy of tomes, so if the film adaptation actually happens and is a success, we could potentially see four movies if it follows the current trend to split the final book into two films.
Daldry is normally found making more grounded dramas, so it would certainly be interesting to see what he does with a fantasy adaption, especially given his theatrical background. His current project is The Crown for Netflix, a series adapting Peter Morgan's (Frost/Nixon) play The Audience, which chronicles the Queen's meetings with prime ministers through the decades.