EDIT: found it at the end of the article
" For anyone interested in learning more about the life and work of John von Neumann, I especially recommend his friend Stanislaw Ulam’s 1958 essay John von Neumann 1903–1957 in the Bulletin of the American Mathematical Society 64 (3) pp 1–49 and the book John von Neumann by Norman Macrae (1992). "