There is no historical proof that Albert Einstein wrote a book titled "God vs. Science" in 1921. The "God vs. Science" argument originated in an email chain and has never been definitively linked to Einstein.
Albert Einstein was a German theoretical physicist most known for his general theory of relativity and his mass-energy equivalence formula. His religious beliefs were not that of a personal God, but he followed Spinozism, which sees God as a singular self-existing substance.
In 1940, Albert Einstein penned an essay titled "Science and Religion," but there is no evidence to suggest the "God vs. Science" argument was his work.