Hugo Steinhaus: Wspomnienia i zapiski (Memories and notes), (published posthumously in Wrocław, 2002, 1st edition by Aneks, London, 1992).
To my knowledge, not available in English, but there is a German translation:
Erinnerungen und Aufzeichnungen, Neisse-Verlag, 2010
Personal life, mathematics (with motivation and solution of some problems), interaction with other mathematicians (including Stefan Banach, Bronislaw Knaster, but also Steinhaus's students Stanislaw Ulam and Marek Kac, whose autobiographies are listed here, and many others), academic environment in Poland, World Wars I and II, rebuilding of Western Borderlands after 1945- very engaging and insightful (if sometimes opinionated) writing, little "navel-gazing". And not so easy to google up if you did not already know about it, even if you read Polish.
Updated in 2020: After this answer was posted, an English translation appeared (not that soon):
Mathematician for All Seasons: Recollections and Notes, Birkhäuser
Volume 1 (1887-1945) (Vita Mathematica 18), 2015
Volume 2 (1945-1968)
Vita Mathematica 19, 2016
Translated by Abe Shenitzer, edited by Robert G. Burns, Irena Szymaniec, and Aleksander Weron.