But once our heroine arrives in Parliament there is plenty of material for historians. And unlike volume one, it is not served up in homogenised form.
Even so, and tantalisingly, there is too little insight on the author's mind, her private calculus and apprehensions. David Frost, that silkiest and most intelligent of interviewers, drew last night from Margaret Thatcher the admission that as a child she always preferred the conversation of adults. And that she liked solitary walks. (As a matter of fact, I don't think this second claim is true - unless she is thinking of a Gladstonian ramble along the pavement. Mrs Thatcher had no appreciation of Nature's force or beauty.)
But what was going through her mind, not just then, but later? We get hardly a clue. And so the principal conundrum remains. How did this pretty, innocent girl, whom some photographs depict with just a trace of mischief showing in her glance, get to outmanoeuvre the whole Tory establishment? How did she manage first to penetrate, then carve up, the piggiest, pastiest core of male chauvinism outside the T & G?
What actually was going through her mind when she chaired the first meeting of the Shadow Cabinet in 1975, not one of whom she had appointed herself and for many of whom she must have felt a combination of distaste and contempt, moderate only by comparison with what they were feeling towards her? "As a new Leader, of a shaken and still badly split party, and as a woman striving for dominance in this noisy, boisterous, masculine world, I could expect difficulties ahead." But when she became Prime Minister, what happened? All the old Heathite heavies were kept on, and blighted the first two years of her administration. Was this nervousness, diffidence - or cunning?
Sometimes the code in the text is so faint that you need a cipher clerk. For example, the book is most generously illustrated. There are 94 black- and-white plates depicting every stage and episode, it seems, from her life. Dignitaries, from Ronald Reagan to HM the Queen Mother, are seen in the author's company. The Queen, however - who displayed towards Mrs Thatcher jealousy, contempt and spite, arranged for her to be humiliated whenever this was practicable, and periodically essayed to make political mischief - is not depicted. The book is 647 pages long, but the references to Her Majesty in the index (both of them indirect) are but two in number.
Sometimes the code is less opaque. Of reappointing Ian Gilmour, "... I felt that he could make a useful contribution as long as he was kept out of an economic post ... to which neither his training [sic] nor his aptitudes suited him." On occasion - very rarely - the mask slips altogether: "It [read the book to find out what] ... showed many people from modest backgrounds like mine how close to the surface of the Tory grandees lay an ugly streak of contempt for those they considered voting fodder." At other times there are trace elements only: "I generally had polite [uh?] and pleasant relations with my other colleagues [in Ted Heath's first Cabinet] but I knew that we were not soul mates." And there is a certain sly sense of humour, or parody: "Jim Prior [they loathed each other] was Agriculture Minister, a post which his farming background and rubicund features helped him make his own."
A failing (one of many) in volume one was the avoidance of any disclosure concerning her relations (emphatically not relationship) with Willie Whitelaw. But now we read that "our strengths and weaknesses complemented one another's".
Say that again. Weaknesses? Not much mention - indeed I couldn't find any - of hers elsewhere. What can she be referring to?
An objective reader will find them on display in the last part of the book, where there is a positively Bourbon "overview" of current affairs. Of geostrategic vision there is none - simply a tenacious recital of the idees recues of the Cold War. And the World War(s), come to that. Her attitude to Europe is conditioned by a refusal to understand the Gaullist concept of the patries; that Germany must be seduced, France reined back; the northern, Hanseatic, countries separated from the mendicants of the south who trade their votes in the Council for wedges of "convergence" money.
All the same, at the conclusion of the Frost interview it was impossible to avoid the judgement - that person could still win a general election.
The last time I had a serious talk with Margaret Thatcher was after the Gulf Memorial Service in Glasgow Cathedral, more than four years ago. To her I said, "Whatever you do, don't leave the House of Commons. Just stay there. Don't say anything. Just vote on three-liners. But don't abandon us." In truth, I don't know if this advice was even practicable, given her character, her burning sense of injustice, her hunger for international acclaim and hefty appearance fees, and the partial promptings of her various courtiers - among whom I have never myself been included.
But of this I am certain from my own long, both practical and genetically based intimacy with of the Conservative Party: had she done so, stayed silent, behaved with dignity, nurtured the sense of timing and opportunismshe showed in 1975, Mrs Thatcher would again be Prime Minister today.
As it was, Denis came over and interrupted us. "Over my dead body, Clark. Be off with you."
And I departed. Was Denis wrong again, just as he had been in 1975? The book records his verdict on being told by Margaret that she was going to challenge for the leadership: "You must be out of your mind. You haven't got a hope." Of course he was speaking personally, not politically.
But even politically, and weighing up all things - in particular those "convictions" both openly proselytised and unconsciously revealed in the second half of this work - I'm not so sure.
'The Path to Power' by Margaret Thatcher (Harper Collins, pounds 25)