Just over a year ago, I went to Mohamad Mahathir's office on the 86th floor of the Petronas Twin Towers to interview the former Malaysian prime minister about Barry Wain's recently published biography of him. It was a frustrating business.

I suggested we begin by talking about "the book." He claimed not to know which one I was talking about – even though the media in Singapore and Kuala Lumpur had been full of it for weeks, not least because at that point the Malaysian authorities were not letting it into the country. So I held up a copy of Malaysian Maverick. "Ah," said Dr M. "Barry Wain. All the bad things I did throughout my 22 years. Nothing good at all." He smiled. "If that is his impression of me, he is welcome to it."

I had hoped for some feisty rebuttals of the charges Wain laid against him. This is a man, after all, well known for his pungent put-downs. Indeed, to his admirers (and with qualifications, I am one) his outspokenness is one of his most attractive qualities. But when it came to the key queries, which will be familiar to anyone who has considered his years in office (1981-2003) – the growth of corruption, the emasculation of the judiciary, the retreat of secularism, the silencing and imprisonment of critics – he was fluent, but ultimately evasive.

Those hoping to find satisfactory answers in Mahathir's long-gestated 800 page memoir, "A Doctor in the House," will be similarly disappointed. For one of the amusing aspects of this book (although those who have suffered some of the good doctor's harsher ministrations may not find it so), is that when it comes to the main incidents his critics have always latched on to, it seems that Dr M wasn't there.

When 106 people were arrested during 1987's Operation Lalang, he tells us, "I was flabbergasted... I thought only a few ringleaders would be taken in... But I could not countermand police orders." Mahathir admits that his finance minister, Daim, "was repeatedly accused of lining his pockets and taking kickbacks from contracts." But what could he do? "People came to see me to complain about him, and when I demanded evidence, they could produce none."

As for the dismissal of Tun Salleh Abbas as Lord President of the Supreme Court the following year: it had nothing to do with his criticisms of the government or his lack of pliability. "It was the Agong who instructed me to remove Tun Salleh," writes Mahathir, explaining that the then king felt insulted because Salleh had written to him complaining about noisy building renovations. Dr M realizes that some readers will be "incredulous" that he "was prepared to dismiss the Lord President simply at the Agong's behest and on his personal demand... But that is the truth as to what happened."

He rues the fact that he has been "branded a legal vandal" as a result. However, "many see only what they wish to see.... for me that is simply human nature and it has to be accepted."

In 1998, Dr M says he was "apprehensive" when the police told him they were going to arrest Anwar Ibrahim – with good reason, since his former deputy then appeared in court with a black eye. "I advised the IGP not to use violence or to handcuff Anwar," he writes, "...it angered people when I suggested that his injury may have been self-inflicted, but I honestly did not think that the police would beat him up, particularly after I had personally instructed the IGP to be careful."

He expresses irritation at the way Anwar's trial was conducted, meaning his former protege was "able to score several points and leave many Malaysians convinced that he was the victim of a political conspiracy." But, continues Mahathir, "how anyone could believe this, I really could not understand. To conspire against Anwar in this way I would have had to take the police, the Attorney-General and his prosecutors, their witnesses, the judge, the forensic laboratory experts and many others into my confidence."

The problem for Mahathir is that there are many who believe that he was perfectly capable of doing that; or at least, if he did not issue orders personally, that he presided over an administration in which people knew what outcomes he desired and made sure that nothing got in the way. He almost concedes this possibility at one point: "Like it or not, I must accept that this is what Malaysians are like. When you are the top man people will try to read your mind and try to do what they believe you want."

This rueful, seemingly powerless stance sits very oddly with a man whose entire career has been marked by such commendable attention to detail that he could even find the time when prime minister to look into why Kuala Lumpur's street lamps did not appear to be properly lit. (Their ill-fitting covers were letting in insects, whose frazzled remnants then obscured the lights. "I pointed out the problem to the Datuk Bandar [mayor] and soon enough the covers were cleaned, and more importantly, kept clean.")

His enthusiasm for efficiency, simplification of bureaucracy and ensuring implementation of decisions are well detailed in his memoirs, and no one can doubt that they were needed. Once, when Dr M liked the idea of building a replica of Rome's Spanish Steps near the KL Tower, the Public Works Department despatched a team to study them. Unfortunately, "they could not find the Spanish Steps... because they were sent to Spain".

Many will continue to find it hard to believe that one of the most determined and forceful premiers of the late 20th century, who can take much of the credit for pushing and often, it seemed, dragging Malaysia towards developed nation status, willing great construction projects such as the Penang bridge and the Twin Towers into being, and with the strength of personality to stick two fingers up to the IMF during the 1997 Asian financial crisis, could not have known exactly what was going on at every level of his administration.

The questions over what Mahathir describes as a "black mark" (Operation Lalang) and other incidents – he recognizes that Anwar has "demonised" him "in the eyes of the whole world" – will not go away and will cast a shadow on his reputation for as long as historians care to examine it.

In a wider context this matters a great deal, for while many Malaysians may be ambivalent about their longest-serving prime minister, nearly all of them acknowledge that his achievements were considerable – game-changing for Malaysia, in fact – as well the fact that other aspects of his record were not so creditable. Abroad, however, and especially in Europe and America, the "black marks" are just about all anyone hears about.

This is a great pity, as for those who wish to listen Dr Mahathir has highly interesting things to say. His chapter on "The Europeans", for instance, is written from a fascinatingly revisionist perspective – but contains much that one cannot disagree with. He believes that the European taste for warfare fed into the 20th century religion of the market and "the idea that competition will not only establish who the winner is but who is right". A false connection, as he says: "Already they are seeing disaster in their own countries as the free markets wreak havoc on their finances." Pointing to the deaths accompanying new systems of government in Europe (by which he means the world of the white man) over the centuries – republicanism, Communism etc – he claims this stems from the insistence that any new ideology was the best.

"They would not only practice the system but would want to force everybody else to do the same. Many who refused would be killed.... Currently they believe that democracy, the free market and a borderless world will create heaven on earth...They invade countries and kill people in order that democracy and its accompaniments be accepted by all."

Who can dispute that after the last decade? Again and again, his criticisms of Western hypocrisy hit home, such as his argument that there is nothing equitable about global trade agreements that allow rich countries to penetrate and dominate developing nations' markets, while continuing to subsidise their own industries at home.

On Islam, too, if the Western world could temporarily suspend its sensitivities about any mention of "the Jews" (with whom, regrettably, Mahathir does occasionally manage to make himself sound obsessed), they would find much to applaud in what he has said. Repeatedly he has urged his fellow Muslims not to be taken in by literalism, medieval obscurantism and a concentration on the afterlife that ignores the plight and lack of progress of their co-religionists in this world. He claims that it is Islamic to be pacific, to be moderate, tolerant and to seek knowledge.

The academic Patricia Martinez once wrote: "In his pragmatic understanding of and agenda for Islam and its umma, Mahathir was the best contemporary leader in the Muslim world." It may be that it didn't quite work out like that at home – in my interview with him, the one point he conceded was that the pressure to be seen as "Islamic" may have grown during his premiership – but Martinez's point still stands. Credit is rarely paid him for that, but it is owed nonetheless.

In a book this length many will find smaller details to seize upon and hold against its author. Already some of have attempted to make hay with his comments about the extent of his Indian ancestry (only in Malaysia could this be considered quite so crucially important). His generous remarks about Anwar and Tengku Razaleigh – if they had played their cards differently, he says, the former should have been prime minister and the latter could have been deputy PM – will no doubt be seen by others as fake.

But clearly written, with dashes of humor and of remorse, "A Doctor in the House" is a very readable account of a remarkable politician's life and career as he sees it. Both in length and in span, it bears comparison with the memoirs of his old sparring partner, Lee Kuan Yew, and will likewise be indispensable to future students of Asian history. If at the end of his book, Mahathir remains an enigma and does not solve the riddle of how he could have been such an impressive leader and simultaneously stand accused of so many misdeeds, then that has been his choice. For that at least, he is certainly responsible.

Sholto Byrnes is a contributing editor of the New Statesman and divides his time between Kuala Lumpur and London.