Throw in the sheer tonnage of think pieces and appreciations and other navel-gazing and you’d be forgiven for asking: Do we also need a book about Lorne Michaels? Somehow, despite all of the above, Susan Morrison’s “Lorne: The Man Who Invented Saturday Night Live” — out Tuesday — emerges as indispensable,

At the end of the Feb. 16 broadcast of “ SNL50 ,” a tribute to the half-century reign of “Saturday Night Live” over American culture, Martin Short thanked executive producer and series creator Lorne Michaels, calling him “the man who made our dreams come true.”