An answer like the one given in the above mentioned book does not address the core questions on the holocuast. This does NOT mean there is no answer. I just don’t see how the answer given by the above mentioned book answers it (which also is not to say that it doesn’t. I just am having a hard time understanding why it would…)
Let’s review the question:
1.) If Hashem can do anything then it is not “necessary” for him to do anything to reach any particular outcome.
2.) Hashem is Kind, Fair, Loving and does not want to cause any pain that is not necessary.
3.) Why and how does it make sense that he would cause such unimaginable suffering as was seen in the Holocaust when he is capable of reaching whatever outcome he desired without causing that suffering?
Saying simply “he did it because he wanted to wake up Klal Yisroel” or “he did it because he said he would if the yidden did aveiros” does not seem to answer the above question at all.