I've repeatedly seen that Stephen Ambrose isn't respected much for his historical accuracy. That he's a great storyteller, but mostly relies on U.S. soldiers who (obviously) can only give their side of the story, but also might have failing memories. How do historians feel about David McCullough? I'm currently reading his bio of Truman, and it's a great read. But I'd like to know how trusted it's details are.
Speaking from personal experience, I would say he's the same. My parents' gave me his bio of Madison because my mother loved it so much and I had to stop because he never really critiques his sources, randomly drops quotes without context, and is overly concerned with telling his story than actually getting at history.