At over 600 pages (including a 28 page index and 100 pages of grrrr endnotes), this book is nothing if not comprehensive; but it covers only the first 41 of Heinlein's 80 years, ending neatly on the day of his third marriage. We learn of Heinlein's liberal Missouri family background, his career in the Navy dashed by ill-health, his dabbling in political activism (as a left but libertarian Democrat in the 1930s) and his early writing career, and rapid emergence as a leading light in the world of sf. It's all told in meticulous detail.
However, the hagiographical tone of Patterson's introduction is a warning signal that the book may perhaps have too narrow a focus on its subject rather than on his environment. Heinlein's death is compared to the Kennedy assassinations and 9/11 in its impact on people"s lives; we are told that he "galvanised not one, but four social movements of his century: science fiction and its stepchild, the policy think tank, the counterculture, the libertarian movement, and the commercial space movement." It's news to me, as one who has been active in both, that policy think tanks are especially closely linked with sf in their historical origin.
As did Jo Walton, I had hoped for a biography that would both get under Heinlein's skin and contextualise his work in the politics both of the USA and of science fiction of the times. But you will learn more of Heinlein's politics by reading half of Ken MacLeod's essay in The Cambridge Companion to Science Fiction. This book is almost entirely surface detail - microscopically mapped and decently structured, but it will be an indispensable secondary source for other, better works in future.