Dialectic of Enlightenment crystallized a lot of thoughts in me around critical theory and philosophy in general. Before that book the closest I had ever been to philosophy was John Gall's excellent "Systemantics" which although wonderfully written and a delightful read didn't leave me with much insight into how to actually critically examine my surroundings. Dialectic of Enlightenment on the other hand left me with some basic tools I can apply to understand my surroundings, some understanding that the problems faced by a system (society) echoes the features of that society. That the ills we feel are the ills we create.

Dialectic of Enlightenment convinced me that philosophy itself is actually useful and constructive, rather than just a pointless navel gazing activity.