I've never been to Sleep No More, but from what I've read about it, I imagine this book is Sleep No More ramped up to the tenth degree.
There were a lot of characters in this book, a lot of imaginative histories and stories woven into the tale of this circus and its performers. But in the end, I felt the foundational plot - a training competition between rival magicians that uses two star crossed lovers as pawns - to be the unbelievable bit in this lovable and credibly strange, eccentric world. I also found the 'normal' humans of the book to be more compelling than the circus performers - they had hopes and dreams and fears and histories, whereas many of the sensual freaks portrayed throughout had nothing but charisma and talent to pull them through the text.
For example, the young boy who runs away with the circus has a family who does not understand him and a sister who is cruel. The clockmaker who designs the clock and who becomes so obsessed with the circus so as to become the leader of a cult of followers seems more endowed with humanity than the contortionist who is throughout referred to as mysterious and tattooed, but whom we only learn at the very end suffered a tragic romantic loss that gave her a purpose within the plot.
So the book became an exercise in imaginative writing, more so than compelling storytelling.