Where were conditions like in the concentration camps?

Conditions in the camps were brutal. Frankl writes about the starvation rations, the impossible living conditions, the brutal manual labor he was forced to perform, the poor clothing and bitter cold, the beatings, the daily confrontation with death. He talks about how one becomes hardened to even the most abject or terrifying scenes; how the purpose of the camps was to separate the prisoner from his humanity, to turn them into numbers.
Despire all this, the thesis of Frankl’s book is that if one has a purpose in life, one can endure anything. For all the horror of the camps, Frankl also writes about the decency of the prisoners, of how even in the camps it was possible to show compassion or friendship. Mostly, though, Frankl argues that the people who best survived were not the physically strongest ones, but the ones with the will and imagination to live. For Frankl, the memory of his wife, and his ability to remember her love for him and imagine being in conversation with her, keeps him alive. Her memory keeps him from breaking down, and the hope of seeing her again gives him purpose. In a way, conditions in the camp make possible a certain clarity of thought; his experience teaches Frankl that there are some things—his memories, his fundamental humanity— that cannot be taken from him.

In Man's Search for Meaning, Victor Frankl describes conditions in the concentration camps as brutal and dehumanizing. He notes that the truly good people didn't survive, because it took a certain level of ruthlessness to make it from day to day.
Frankl writes about the three phases inmates went through: the first was disbelief that this was happening, and the second was the end of empathy or emotional response to what was going on. In the second phase, an inmate simply became numb to people being beaten, tortured, or killed. The third, for some people, was just giving up and waiting to die.
There wasn't enough food in the camps, so people became emaciated and lost muscle tone. It was cold much of the year, and yet the inmates, despite the harsh conditions, tried to look healthy because they feared that otherwise they would be sent to the gas chambers.
Frankl talked about working in the infirmary and hearing the thud, thud, thud of the heads of dead bodies bumping along as they were dragged down the stairs and flung outside. 
Frankl's point, however, is that despite all the horror, even in the camps there was some minuscule sliver of life that was not permeated by the hatred.