As Pope Benedict XVI's controversial new book is snapped up in bookshops, Vatican experts say he has cast off his reputation as a conservative "rottweiler" in favour of a more compassionate image.

From condom use to child abuse, the burqa and female ordination, Benedict talks candidly in "Light of the World" about the polemical issues that have marked his pontificate since April 2005.

The book is "the fruit of repeated crises" in the Church's relationship "with Jews, Muslims and also with public opinion on delicate issues such as paedophile priests and condoms," Vatican expert Marco Politi said.

With this collection of interviews, the 83-year-old Pope hopes to open a "new channel of communication with the world," Politi added.

Benedict caused a global outcry on a trip to Cameroon last year when he said condoms would "aggravate" AIDS; in an apparent about-turn, he now says they can be used "in some case" to prevent the spread of disease.

"It's a considerable step forward," said Politi. "It's the first time that a Pope accepts condom use this clearly, even if a number of bishops and cardinals had already said so."

Sandro Magister, who covers the Vatican for the Italian news weekly l'Espresso, said: "the book completely demolishes the image of retrograde, ultraconservative Ratzinger."

"He shows a desire to understand the world. The only example he gives for condom use -- that of a sex worker -- shows his goodness, even towards sinners," he added.

The German Pope also makes tentative inroads into delicate issues such as banning divorced people from receiving communion.

But analysts said the Pope fails to address important topics that drive modern society.

The Church still views sexuality as a means to an end -- procreation -- and contraception is taboo. Homosexuality is denounced as immoral whilst female ordination is simply out of the question.

However, far from living up to derogatory nicknames conjured up for him by critics such as "Panzer Cardinal" or "Grand Inquisitor," Joseph Ratzinger admits he doesn't know all the answers, and is sometimes even afraid.

He openly acknowledges that his speech at Regensburg on Islam and violence that sparked religious riots was "more academic than political," and claims that Catholics and Muslims are "on the same side of a common battle... the defence of major religious values."

And above all, Benedict says he is aware of his weaknesses, even tackling the subject of a possible resignation "should a Pope realize he is no longer physically, psychologically and spiritually capable."

"These are questions that had already been addressed by Paul VI and John Paul II, but always in a very muted way," said Politi.

"For the first time, a Pope is publicly considering not being elected for life, if he feels he no longer has the strength to lead," he added.

German journalist Peter Seewald, who wrote the book based on 20 hours of interviews with the Pope, describes the Benedict he met as "old, tired and weighed down with a heavy workload," adding another layer of meaning to the pontiff's admission that the job is not always for life.