Goblin Secrets, by William Alexander, Margaret K. McElderry Books, New York, 2012.
This is a very good book. It is written about the same city and situation as Ghoulish Song. I really enjoyed it. Graba was as evil as she could be, but in the end, she was not the truly evil person. She was also very powerful as an old witch who had been around for a long, long time. However, her image sister has taken the route of a goblin, or a changed one. She too has a great deal of magical powers, but in a different route.
The river is rising. Someone must talk to the river, and convince him not to flood and injure people. The goblins have protected the city for many years, but because of personal bias, they have been excluded from the city and cannot talk for the city. Rownie must find his brother Rowan, to him talk to the river for the city. Rowan is good at wearing masks, but he disappeared several months ago and no one has seen him.