This book actually contains two novellas (The Mad Baron's Mechanical Attic & The Choir of Knives) and they together tell the story of how Locke, Jean and the other gentleman bastards acquired the Austershalin brandy that played such a key role in the con at the centre of THE LIES OF LOCKE LAMORA. We will also find out how they managed to avoid being killed by the elite assassins known as the Choir of Knives.
Basically what we get is the backstory of the Bastards and a chance to discover how Locke and Jean forged their gang. Gollancz say that the books is perfect introduction to new readers. Lengh is report to be around 100,000 words (336 pages)