Schlink is right. The Reader isn't about the Holocaust, it's about the effects of illiteracy; however, we would be remiss if we didn't mention the guilt that the Holocaust leaves behind (as it ultimately results in Hanna's death).
First, let's look at the effects of illiteracy in The Reader. Hanna Schmitz is illiterate, but we don't find that out right away. We first meet Hanna as she helps Michael home after an attack of hepatitis. Even though Hanna is twice Michael's age, the two begin a love affair with each other. At this point, Michael is in high school and Hanna is a street car conductor. As Michael begins to neglect his studies in order to see Hanna, she reprimands him and absolutely insists he do well in his classes (here stands the first clue she is illiterate). As Michael complains about how much reading he is given, Hanna asks Michael to read to her (yet another clue). As their relationship continues, there are more clues to Hanna's illiteracy such as Michael's "job" of coordinating the details of a bike vacation, the note that Michael left for Hanna that was "lost," and Hanna longingly running her fingers along the book spines in the library. Eventually, Michael makes other friends and refuses to acknowledge Hanna's existence at the pool one summer. Hanna vanishes.
Michael sees Hanna years later when she is convicted of war crimes as an SS officer in Germany. Michael listens as Hanna is accused, but Hanna refuses to admit that she wrote the condemning report. When her fellow SS officers insist that she did, the judge is about to call in a handwriting expert when Hanna strangely changes her tune and says she wrote it. This is the exact moment when Michael learns Hanna is illiterate.
But could Hanna's shame at being illiterate be sufficient reason for her behavior at the trial or in the camp? To accept exposure as a criminal for fear of being exposed as an illiterate? To commit crimes to avoid the same thing?
Michael is too ashamed to stand up for Hanna, so Hanna gets life in prison.
The question is as follows: does Hanna get life in prison because of her illiteracy or because of her Holocaust war crimes?
Michael eventually sends Hanna tapes of him reading famous books. As Hanna writes him back (proving that she can now read and write), Michael only responds by sending more tapes of readings. When Hanna is about to be released, the prison contacts Michael to ask him for help with Hanna's assimilation. Michael begrudgingly agrees and is turned-off by Hanna's now haggard and heavy appearance. Hanna is hurt. Michael agrees to come and get Hanna on her release date, but she hangs herself the night before. As Michael looks at Hanna's cell, he finds many books that she had now read about the horrors of the Holocaust... horrors that she participated in (even if indirectly).
The second question is as follows: does Hanna hang herself because her newfound literacy revealed the truth, or because she feels intense guilt over her Holocaust involvement?
If you haven't figured it out yet... there is no right or wrong answer here. Illiteracy is one of the implied reasons Hanna had to take a job with the SS. She left her job as a street car conductor in fleeing (in hurt) from Michael. Illiteracy is one of the implied reasons Hanna is given life in prison. It "makes" her falsely admit that she wrote the damning report. But what of Hanna's Holocaust involvement?
Hanna's involvement in the Holocaust as an SS officer involves the burning of a church. Hanna's job was to bring prisoners back and forth between concentration camps. During this job, she was ordered by her superior officers not to open the doors of a church where prisoners were kept. Unfortunately, the church was bombed and was burning. All the prisoners were killed except for one mother and daughter who are there at the trial to condemn Hanna.
In conclusion, we must understand (as readers) that the Holocaust specifics here are included in order to take a back seat both to the relationship of Hanna and Michael as well as the illiteracy of Hanna. It is implied that, if Hanna could read from the beginning, she would have been reading the books that might have interested her, learned about the Holocaust, and never willingly enlisted in the SS.
Now to escape involves not just running away, but arriving somewhere.