Louis Armstrong was a giant of 20th-century music: the pioneering innovator for both jazz instrumentalists and vocalists. A star of radio, film, television, and the concert stage, he was also jazz’s global ambassador. In his narrative biography, Pops: A Life of Louis Armstrong (Houghton Mifflin Harcourt, $30), Terry Teachout (drama and jazz critic for the Wall Street Journal) draws upon the 650 reels of Armstrong’s personal “audioverité,” reel-to-reel tapes for the first time to reveal the real man behind the affable public persona. Teachout gives us Armstrong’s “epic journey from squalor to immortality,” and shows us his joyous, radically transforming art in all its complexity.