His "Dictionary of the English Language", published in 1755 was the standard for over 150 years, and that alone gives him enormous standing in the English speaking world. The book however is more attuned to the attempt of understanding what Johnson's life and thoughts were really about, and he was quite an interesting person.
Born sickly, possibly with Tourette syndrome, to a father deeply in debt for most of his life, Samuel's life had many difficulties. He was large and apparently quite homely, but also when not depressed or ill, quite vigorous. He was a devout man, but like all mankind, subject to temptations of sloth, excess and lust. Since he was a man of letters, diaries, written prayers as well as pamphlets books and plays as well as the subject of a number of biographies, we have a good deal of insight into his private life.
There seems little doubt that he was a genius of literature, able to read, comprehend, editorialize, and maybe most famously, produce the short pithy quotation:
Almost every man wastes part of his life attempting to display qualities which he does not possess.One could go on forever with such quotes, he was a master of insight and language.
Bachelors have consciences, married men have wives.
Dictionaries are like watches, the worst is better than none, and the best cannot be expected to go quite true.
Every man is rich or poor according to the proportion between his desires and his enjoyments.
In 1763, he formed "a Club", a social group that included his friends Reynolds, Burke, Garrick, Goldsmith and eventually Adam Smith and Edward Gibbon. They met Mondays at a pub called the Turk's Head in Soho ... a most august group of men of the era, and a testament to the intellectual standing of Johnson.
While brilliant, given his infirmities and difficulties with love and money, his life was a more or less constant challenge -- but to some degree, it does the heart good to listen to all his difficulty and realize he still lived to a ripe old age, and accomplished a good deal in that life.
Knowledge of Samuel Johnson is pretty much a requirement for a person minimally educated in English literature -- I'm not learned enough to say if this work is a decent competitor to "The Life", but I found it well done, and Mr Nokes reputation precedes him.