Niels Bohr was one of the giants of twentieth-century physics. He and Einstein respected each other very much, but their work habits were just about opposite. Einstein preferred to work with just a single assistant, if at all, whereas Bohr worked very hard to secure funding for an institute of theoretical physics in Denmark. Bohr was successful in creating a centre that attracted top young physicists from around the world, who (thanks to funding from the makers of Carlsberg Beer) were able to each spend a year or more being mentored by Bohr.
A great biography of Bohr (including a significant amount of high-level physics) is Abraham Pais‘s Niels Bohr’s Times. One of the most memorable and moving episodes in this book is the heart-breaking description of the events surrounding the death of Bohr’s eldest son.
However, a thoroughly delightful book at a lower level of difficulty is George Gamow‘s Thirty Years That Shook Physics. It’s available as an inexpensive paperback, and is accessible to students who have finished first-year university physics, and to some high school students. It’s the perfect book to read before second year “modern physics” courses, as it explains the historical development of some of the basic ideas of quantum mechanics, but weaves in anecdotes about the great physicists whom Gamow rubbed shoulders with. Gamow seems like a very fun-loving man, and many of the anecdotes are hilarious. Gamow also wrote the “Mr. Tompkins” books, which are widely acclaimed, and other wonderful science popularizations.
The Bohr anecdote that is my favourite is recounted by Gamow on pages 57–58 of the Dover edition of Thirty Years That Shook Physics:
There is another amusing story illustrating Bohr’s whimsey [sic]. Above the front door of his country cottage in Tisvilde he nailed a horseshoe, which is proverbially instrumental in bringing luck. Seeing it, a visitor exclaimed: “Being a great scientist as you are, do you really believe that a horseshoe above the entrance to a home brings luck?” “No,” answered Bohr, “I certainly do not believe in this superstition. But you know,” he added with a smile, “they say that it does bring luck even if you don’t believe in it!”
For a person who believed very deeply in the principle of complementarity, this must have been a deliciously paradoxical horseshoe!