He recognizes Mencken's unparalleled skill as a journalist, his remarkable work on The American Language and a New Dictionary of Quotations and his masterpieces of style, Happy Days and Newspaper Days.
But he also concludes that much of Mencken's social criticism amounted to nothing more than a "Punch-and-Judy show," and that he was, in many ways, a lousy editor who ran roughshod over writers and published magazines that were often dull.
He points out that Mencken's relentless attacks on those he considered his intellectual inferiors -- the nation's Puritans, pedagogues and Babbitts -- helped liberate American culture, especially literature.
But he also demonstrates that Mencken's philosophy was often contradictory or poorly thought out, and that the man who edited the nation's most influential magazines of ideas showed astonishingly little interest in the artistic and cultural developments of his era.
He shows readers the Mencken who is gregarious with friends, devoted to his mother and brother and tender with his wife.
But he also deals frankly with the man who was a radical in public and a Victorian in private, who judged colleagues "mercilessly" in his diary and who was, without equivocation, an anti-Semite.
It is undeniable that Bode and especially Hobson cover ground Teachout leaves untouched. One important example is that Hobson explores Mencken's attitudes toward African-Americans, which Teachout glides over.
But the bottom line is that Teachout understands Mencken better than any other biographer -- so much so that, in retrospect, it is surprising that Hobson didn't make better use of all the new material available.
Equally important, the Mencken of Teachout's biography is a real man -- warts and all -- not an icon. Biographers tend to choose subjects they admire, and too often that colors their work.
Teachout manages the difficult trick of admiring the traits that made Mencken great -- his incomparable work ethic, his lively mind, his gorgeous prose style -- while being unfailingly honest about his shortcomings.
There was, as Teachout puts it so aptly, "nothing small about him, not even his flaws."
In the end, Teachout offers an assessment of Mencken that rings true: "He was to the first part of the twentieth century what Mark Twain was to the last part of the nineteenth -- the quintessential voice of American letters. Perhaps even a sage, of sorts, too, though an altogether American one, not calm and reflective but noisy as a tornado; witty and abrasive, self-confident and self-contradictory, sometimes maddening, often engaging, always inimitable."
This will not be the last biography of Mencken -- another is already in progress -- but Teachout has set the bar extremely high for writers who come after him. Indeed, with his penetrating insight into the man and his work, Terry Teachout may already have had the final word on H. L. Mencken.
Stephen R. Proctor is the Sun's deputy managing editor for features and sports. He has worked for The Sun for 22 years, and for his entire adult life has been a serious student of the history of this newspaper and The Sun's most famous writer.