I don’t really have one off the top of my head. I would not describe myself an expert despite my experiences. I was quite young at the time so of course my perspective is biased by my family.
Honestly, the first book I remember reading on the subject of Nazi Germany was one of Haffner’s but I’m not sure which it was. So, I suppose I’d recommend his other works.
I have a few books I would not recommend as I personally found them to be at best sympathetic to Hitler, and at worst, even supportive. The notorious book by Kubizek, The Young Hitler I Knew is, at the very least, an interesting read though I believe it is more a nostalgic and overly romanticized account of what Hitler had been like. If not watered down propaganda fluff. A more romanticized and fictional account would be Gerber’s The Life of Adolf Hitler which reads more like a novel than a biography.