Cloaks and Shadows is one of my favourite modules. It is investigation heavy, though there are more than enough clues to lead you to the end with ease. The vast majority of fights (all but 2) can be circumvented with clever roleplaying and the module actively encourages you to avoid combat and keep a low profile. The boss of the module is particularly fun, using a trick to cover his tracks which inspired many of my players to imitate him.