Context:

Referenced as 'a brilliant book on the whole story about King's killer and the manhunt for him.' The book describes the boarding house where the assassin stayed as 'a haven for invalids, derelicts, transients, riverboat workers, and small-time crooks.' Later referenced again when discussing the FBI manhunt being the biggest in FBI history. This is likely referring to 'Hellhound on His Trail' though the title is not explicitly stated.