To answer this question one has to understand the fundamentals of Nazism, as they burned any book that did not reinforce their ideology. The Nazis were a far right organization and positioned in direct opposition to communism, so anything written from a "leftist" perspective was burned. Marx is the obvious example but they are far from the only authors subject to this. Nazism encouraged the use of violence for political gain so anything written supporting pacifism or depicting German history in a bad light was also burned. Books written by individual "traitors" of the state, like Einstein who had fled to the United States and spoke out against Nazism, were burned as well. But most significantly, they burned books written by Jews. All Jewish art, culture, music and literature was methodically banned in the Third Reich.

The Nazis didn't actually burn a lot of bibles. Nazi Germany was not an atheist nation, and churches were allowed to exist under extremely strict circumstances. Like all institutions in Nazi Germany, the churches were used as an appendage of the Nazi state to control the population. If churches resisted they would be brutally suppressed, but those who fell into line were generally left alone. Bibles in fact were never banned in Nazi Germany, and the majority of banned literature opposed the Nazi ideology or worldview, or was written by an enemy of the state or "subhuman race."