He was the only man in Hitler's entourage who sacrificed neither his will nor his reason. He also was a man of great talent who did most to enable the Nazi dream to become a reality.
While he had a special relationship with Hitler, he opposed his scorched-earth policies and plotted assassination. At the Nuremberg Trials, he was sentenced to 20 years. Eloquent in accepting responsibility, his frank statements probably saved his life, in contrast to that of his labor deputy, Fritz Sauckel. While in prison, he wrote a sometimes controversial but informative autobiography, Inside the Third Reich.
Hitler's young architectAlbert Speer had briefly met Hitler in July 1933, to get approvals for drawings for the first Nuremberg Party Rally. That fall, as an aide to Hitler's regular architect, Paul Troost, he worked on the renovation of Hitler's Chancellery. Hitler would chat about the construction, when Hitler suddenly invited him to dinner in his apartment, during which he first asked personal questions. Later, Hitler would tell him,
You attracted my notice during our rounds. I was looking for an architect to whom I could entrust my building plans. I wanted someone young, for as you know, these plans extend far into the future. I need someone who will be able to continue after my death with the authority I have conferred on him. I saw you as that man.
Speer wrote he had found his Mephistopheles, but would have sold his soul for the commission to do a great building. Many believe Hitler saw, in Speer, the architect and artist he wanted to become.
Minister of Armament and Munitions
Speer found it difficult to work with Hitler's decisions. "Like many self-taught people, he [Hitler] had no idea what real specialized knowledge meant....the victories of the early years of the war can literally be attributed to Hitler's ignorance of the rules of the game and his layman's delight in decision making...But as soon as setback occurred, he suffered shipwreck, like most untrained people." Wild decisions were now his downfall. 
For example, when it came to the large-scale Russian campaign, however, he [Hitler] badly underestimated logistics and Soviet resilience. He had an inordinate faith in "secret weapons" to overcome Western industrial dominance. In discussion, however, he often could overpower the actual experts. According to Speer, Hitler, who had an excellent memory, had a catalogue, kept up to date by staff, of the details of weapons and ammunition. When a general would make a strategic argument, Hitler would attack his credibility by showing a small point to be incorrect. Speer observed that true experts do not burden themselves with often-changing details that they can look up, or obtain from a specialist assistant.
When testifying at Nuremberg, Speer said he increased production until he had 14 million workers in 1944. Some of these were prisoners of war and others were forced slave laborers provided by Fritz Sauckel. He also claimed that less than 1 percent were concentration camp inmates.
Wilhelm Keitel was overheard, during Speer's testimony, telling Sauckel, Hans Frank, and Artur Seyss-Inquart that if someone had the courage, in 1943, that the war was lost, much could have been saved. Keitel said that Speer was the only man who could have done so, because he was the only one who truly knew German industrial capacity.  Airey Neave, a Nuremberg prosecutor, said "He was the only man in Hitler's entourage who sacrificed neither his will nor his reason. He also was a man of great talent who did most to enable the Nazi dream to become a reality." Speer would later consider assassinating Hitler, and refused to obey his scorched-earth orders at the end of the war, informing Hitler, at great risk, to his face.
Two Allied specialists who talked extensively to Speer had different views. Psychologist G.M. Gilbert described him as the most reqalistic of all the defendants, realizing that history demands a trial given the enormity of the events, which he considers a "good thing in general. He doesn't think there's any point in bawling about individual fate, although his own guilt is in as much doubt in his mind as anyone else's...He knew no more about concentration camps than any other minister knew about V-2."
"The realization that Hitler was a destructive maniac and not a patriot bent on building up Germany at the expense of others had apparently shattered the illusions of the architect Speer. "
Neave focused more on the justice of the verdict, especially in comparison with that given to Fritz Sauckel. Speer, as an eloquent speaker who took full responsibility, made a far better impression than the less educated, defensive Sauckel. In his conversations with the judges, he found them generally convinced of his sincere repentance, but two still sentenced him to death; 20 years was a compromise. "What has most troubled me is the comparison to the fate meted out to the wretched Sauckel? Why should Sauckel, who procured foreign workers for Speer as Armaments Minister, be the more guilty?...The judges dealt with his case in record time and unanimously sentenced him to death."