Abraham Pais’s Einstein biography is amazing and probably underrated given how hard it is to find in the Amazon search results. I’d imagine his Bohr bio to be equally great.

If a better scientific biography has ever been written, I'd like to read it! Extraordinary history & biography: [Much less technical, but Gleick's "Genius" and Skidelsky's abridged Keynes are also marvellous. (The abridged is better than the full bio.)