The most striking positive that could be derived from the book is that Eliezer lives. The fact that he lives through this ordeal is one positive seen. This is not a triumphant end. It is not something that represents him vanquishing a foe. It is sad because he is alone and his memories of the horror in the Holocaust become his only companion. Yet, there is an overall positive that he lives in the midst of a condition where so many did not.
I would suggest that another positive which is more metaphysical is the composition of the book itself. A positive from Night is Night. The fact that Wiesel does not retreat into silence, but rather speaks about his experience is a positive that arises from the work. Despite the pure terror experienced and the unlimited reservoir of sadness from which the work draws, there is a sense of triumph in the fact that Wiesel was able to share his memoir with everyone. This ability to share voice is a positive from the work as it shows that the Nazi attempt to silence voice inevitably failed. Wiesel's work speaks. This becomes a positive. Even though what it says is representative of tremendous sadness, it is representative of how there is an overall positive in the ability to speak about one's experience and not be relegated into silence.