In 1930, at the age of 63, Laura Ingalls Wilder sat down to write a memoir of her first 16 years.

She had previously written only short pieces for local papers, including a "poultry column" that covered various aspects of rural life (not just chickens). The stream of eight novels for children that soon poured forth, starting with Little House In The Big Woods, originated in this first attempt, Pioneer Girl, written for adults and rejected by every agent and publisher who saw it. The South Dakota Historical Society Press has now produced a lavishly annotated, illustrated and curiously engrossing edition of this previously unpublished manuscript, transcribed from six yellowing writing tablets.

But most of Wilder's tales, familiar from the novels, flop on to these pages in an emaciated state. Saying things to one's own satisfaction isn't the same as reaching the reader. There's a big flatness problem here. Her material seems thrown away, even an epiphany involving "a hovering, encompassing Presence of a Power". The writing's neither dull nor incoherent, just laconic. I like the many lists of songs though, and Wilder displays as usual a spectacular memory of her own childhood and people's names. Since she hardly ever changed one, the book's researchers have verified many of her characters via census records and other genealogists' tools, making this a work of social history as well as a revealing assemblage of Wilder lore.

Anyone hoping to get the real dope on Nellie Oleson, though, or pre-marital shenanigans in claim shanties, or what Ma really thought of Pa and his stupid wanderlust, will be disappointed. I thought Wilder might finally dish the dirt on old Mary too, her too-good-to-be-believed sister, but no; aside from one extra hair-pulling incident, Mary's moral character remains unblemished.

Pioneer Girl shows Wilder in the raw, but mainly as a writer, not a gossiper. Instead of sex and crime, it's full of spelling mistakes, as if Wilder was rushing to get this stuff down, whipped on by her eagle-eyed daughter.

Rose Wilder Lane, already an acclaimed and well-travelled author, nudged, pushed, cajoled and affronted her mom into writing. While brutally dismissive of what she called "juveniles" - children's books - Lane clearly believed in Wilder as a writer, meticulously line-edited her work, got her an agent and publisher and, amid many heated arguments over historical veracity, taught her the fiction game. Lane had been upbraided herself for mixing fiction with fact: as Pamela Smith Hill's informative introduction makes clear, her heavy-handed habit of "fictionalising" real people's lives had earned her many enemies, among them Charlie Chaplin, Henry Ford and the family of the late Jack London. But it may also have made her just the teacher her mother needed.

With Lane's help Wilder learnt how to mould a true story, play around with chronology, build drama and emotion, select a topic for a chapter and stick to it, and render a child's perspective with a word or two.

She became increasingly good, even poetic, at describing landscape and weather, physical crises and sensual experiences, while her own boldness, wit and humility, all in evidence in Pioneer Girl, gave her books their mass appeal.

Lane is quoted here talking abrasively about copy, sales pitches, the book market and how to make a dime, or a name. It's not glamorous, Lane's tastelessness, and their squabbles are troubling, but this was the situation that gave rise to Those Books.

Pioneer Girl is significant in that they both rethought and reworked it, plundered it in fact, for the rest of their working lives. They discussed writing like farmers discuss farming, and even stole each other's seed potatoes: while Wilder relied on a huge amount of editorial help from Lane, Lane snuck elements of Pioneer Girl (at first without Wilder's knowledge or permission) into her own novels, sometimes doggedly paraphrasing her mother's work. The two authors were symbiotically, and certainly financially, entwined.

Wilder's fidelity in later books to incidents mentioned here is maybe more amazing than her lapses, but Pioneer Girl allows you to see a few instances where she strayed from the truth.

In The Long Winter, she depicted the Ingalls family surviving the harsh winter all alone in their house in De Smet. In Pioneer Girl it turns out they had to take in a young couple who stayed for seven months (that's how long the town was snowed in), hogging the food and the fire and never helping out with the chores. Stuck in a blizzard with spongers!

Some adulteration of the facts was done merely to simplify a story line. More worrying is the way Wilder consciously whitewashed the truth, to promote the idea of pioneering as a healthy, heroic American family lifestyle. Pioneer Girl hints instead that this weirdly nomadic clan illegally invaded Indian territory, reneged on railroad contracts, perhaps participated in a vigilante execution, and often lived in close contact with drunks, religious back-sliders, serial-killers and men who shot at their wives, Pistorius-style, through doors, or dragged them around by their hair.

Debt, destitution, starvation and, most despised, government handouts coloured worry-filled lives. Wilder also nearly got raped.

"Then a dreadful thing happened at the saloon! Amy's beau, Hairpin, who had been lying there drunk for several days, came to and took another drink to sober up …

"In lighting a cigar, Hairpin [Hairpin?] then set fire to himself, and died."

None of this made it into Wilder's children's fiction. It would not have appealed to Republicans, nor the makers of the sanitized Little House On The Prairie TV show. But against Lane's advice, Wilder kept Mary's blindness and other hardships, adamant they were crucial to the story.

For a scholarly tome, the cover is appallingly quaint, and this 380-page square book makes a cumbersome object, like a pizza box. But the acres of footnotes are to me a joy. Poor cousins of narrative prose, they're a vehicle for voluminous research and my favourite mode of address: the interjection. But do we need the editors' po-faced response to Ma's sighting of ball lightning? (The Fortean Times has documented such things for years.) Or: "In the nineteenth and early twentieth centuries, idiocy and idiot were the terms used to describe severe cases of intellectual disability"? Thank you. Explaining what scabies is, or "half-breeds" ("people of mixed racial heritage") is also not necessary.

But research on the discomforts of dugouts and sod houses, the settlers' swift destruction of the American buffalo (with some help from the Indians), and the grasshopper plague of the 1870s, is all to the point. And the commentary rightly alerts you to controversies raised by Wilder's depiction of Indians. There's a guilty, colonialist, Gone-With-The-Wind aspect to admiring Wilder's books, after all: though Pa sticks up for Indians a bit, Ma hates them, and so does Jack the bulldog. Yet this pioneer existence of theirs is built on the barely mentioned decimation of native American societies.

Two other spoilers for you: Silver Lake was drained in the 1920s, and the Ingalls gave Jack away. He didn't stay until his dying day. Shucks.