Image copyright Room to Read Image caption Yak to the future: Mr Wood delivered books by yak in Nepal

At some point this year, a child somewhere in the developing world became the ten millionth beneficiary of Room to Read, a non-profit organisation created 15 years ago after a high-flying Microsoft executive quit his job to help children in Nepal.

The charity, which works to eradicate child illiteracy and gender inequality in education, builds libraries and stocks them with books.

It's no surprise that its founder, John Wood, invokes the spirit of the 19th Century library-building steel magnate, Andrew Carnegie.

In a sense, Room to Read has outstripped its spiritual mentor, building 17,500 libraries to Carnegie's 2,500.

It has done so by combining the determination of a Carnegie with the logical, can-do attitudes of corporate giants such as Mr Wood's former employer, Bill Gates.

Mr Wood was on a short break from work back in 1998, trekking in the foothills of Himalayas of Nepal, when the germ of the idea for Room to Read met him head-on.

Locked cabinet

"It really came out of the blue," Mr Wood says. "I wish I could tell you that I was always focused on charitable endeavours, but the reality was that I was focused on myself, on my career, and on how much money I could sock away in my bank account."

Image copyright Room to Read Image caption A library built in Cambodia with books published by the charity in the Khmer language

He was visiting a school in the mountain village of Bahundanda.

It had a library but only a handful of books left by previous visitors. One of them was James Joyce's Finnegan's Wake and another a Lonely Planet Guide to Mongolia.

Moreover, these books were considered so precious that they were kept in a locked cabinet, and never loaned to children. As he departed, the school's head said to Mr Wood that, if he were ever to return to the school, he could perhaps bring a few more books with him.

He knew immediately what he had to do. The empty library had struck a deep resonance with his own childhood experience.

More stories from the BBC's Global education series looking at education from a global perspective and how to get in touch

"I grew up in a family that loved to read and always valued the written word," he says. "I tripped across the right cause in the right place at the right time."

A year later he was back at the same school with 3,000 books. The reaction of the children was confirmation enough that he was taking the right course of action.

Quitting Microsoft

He quit Microsoft to devote himself full-time to literacy in Nepal. Dinesh Shrestha, who had been working on polio eradication for an NGO, joined him and their work of creating school libraries in Nepal began in earnest.

A few months on, another corporate high-flyer, Erin Ganju, who was working in Vietnam, got back in touch with her old friend Mr Wood.

Image copyright Room to Read Image caption John Wood left his job with Microsoft after seeing the lack of books for pupils in Nepal

Soon after, she also quit her job, and these three became the co-founders of Room to Read, a non-profit organisation now working in 10 countries.

Ms Ganju brought a business awareness of the need to build "scalability" into a project - knowing how to make something that works in 10 schools work just as well in 1,000 schools.

Both she and Mr Wood emphasise several "non-negotiables" in the way Room to Read operates.

The first principle is getting the support of the authorities in host countries. "I often say that 'non' in 'non-governmental organisation' does not mean you ignore the government," Mr Wood says.

"We like to work on the basis of a tripartite agreement - Room to Read provides a lot of the capital and the training, the local community supplies the labour and some of the materials.

"The third party is the ministry of education - they provide the teachers and librarians, and pay their salaries. We require them to do this, and we hold them to it."

Local languages

The charity also adheres to basic principles on the ways children are taught. It always works in the language of the local community - even though this often meant publishing their own books and teaching materials.

Image copyright Rish Amatya Image caption There have been 17,500 libraries opened in this global literacy project

It has published over a thousand children's titles in dozens of languages, ranging from Chinayanja from Zambia to Khmer for Cambodia, and from Telugu in India to Xitsonga in South Africa. As far as possible they employ local authors, illustrators and publishers.

It has made Room to Read "one of the biggest publishers of children's books you've never heard of".

Despite his Microsoft background, Mr Wood remains unconvinced about the value of digital technology at this level of education.

Instead, the charity concentrates on the physical, sometimes literally concrete, resources. It has built 17,500 children's libraries and over 1,000 complete schools.

Again, rules apply. The libraries have to meet certain standards. They are typically large enough to accommodate over 40 children at any one time.

Measuring progress

"The books are on shelves at children's eye level, they're not behind glass, there are no locked cabinets," Mr Wood explains.

Image copyright Room to Read Image caption The charity has helped to rebuild schools damaged by Nepal's earthquake

"We have child-sized furniture, child-friendly flooring, posters on the wall, and maps of the world. We encourage children to take books home and we check each week to see how many do."

Everything is closely monitored, statistics are gathered and children's progress is evaluated. This way supporters can be told how effective their support has been.

Teaching methodology is standardised to synthetic phonics, which they believe is the most effective method for children arriving at school with little or no exposure to texts.

Gender equality

Room to Read has a second ambitious goal - gender equality in education.

Image copyright Room to Read Image caption Improving girls' education benefits the whole community, says the charity

The Girls Education programme focuses on the transitional years when girls enter and leave secondary education. There are workshops, life skills camps and help for families with the costs of keeping a daughter in school.

"Providing education for girls is the biggest no-brainer in the world of philanthropy," says Mr Wood.

"Every time we raise £190 we can put a girl in school for a year. If a girl gets educated, she earns more money, she marries later, she becomes more empowered, is taken more seriously by society."

The challenges against girls' education, such as the abduction of schoolgirls in Nigeria by Boko Haram, can seem intimidating.

"Those groups want us to be depressed and frustrated, but this leads to indecisiveness and inaction. The antidote to these forces is action. Let's flood the zone, let's get as many girls into school as we can - that should be our response," said Mr Wood.

Earthquake

There have also been natural disasters. He has been to Nepal to see the damage inflicted by this year's earthquake.

Image copyright Room to Read Image caption Foundations of learning: School building in Tanzania

It had been a heartbreaking experience, but Mr Wood was also inspired by people's determination to continue in makeshift schools. The upshot was an initial agreement to help the government rebuild 66 schools.

Despite such setbacks, Room To Read's founders have ambitions to reach a further five million children by 2020: "Our goal is to work ourselves out of a job."