Adult illiteracy in Indonesia is dropping, but one region has almost a million adults who cannot read. In central Java, one man and his horse are helping improve access to books.

For a formerly wild horse that barely reaches shoulder-height on an adult man, Luna is an unlikely figure to help improve literacy rates in Indonesia.

Luna is looked after by Ridwan Sururi, 42, in the village of Serang, in the Purbalingga region of Java Island.

It is a rural, tropical area, lying on the edge of one of Indonesia's most active volcanoes, Mount Slamet.

In a region dotted by villages, Sururi and Luna has become essential links between communities in recent months.

In January, Sururi started a mobile library called Kudapustaka - meaning 'horse library' in Indonesian.

He travels between villages with books stored in boxes balanced on Luna's back.

He visits schools three times a week - every Tuesday, Wednesday, and Thursday. Sometimes he brings along his daughter, Indriani Fatmawati.

Children and villagers do not have to pay anything to borrow the books and Sururi has not looked to make money from the scheme.

"I love horses, and I want this hobby to bring benefit to people," he told BBC Indonesia.

The idea for Kudapustaka came from Nirwan Arsuka a fellow horse enthusiast and friend of Sururi's. "He asked me: Can we help society through our hobby? I said I was interested, but I didn't know how."

"Then, he had this idea to create a mobile library using horses. I liked the idea, but sadly I didn't have any books. So, he sent me boxes of books."

According to Unesco, Indonesia has made great strides in reducing adult illiteracy in recent years, bringing the number of illiterate adults down from 15.4m in 2004 to 6.7m in 2011.

However, Unesco says there are more than 977,000 illiterate adults in central Java, Ridwan's region.

As a professional horse caretaker, Sururi does not own any of his own animals. So did he ask permission to use the horse as a mobile library? "I haven't," he said, laughing.

"The owner lives far away from this village and hasn't visited the horses for a long time. I am a bit sad about that."

Of the three horses he is paid to look after, Sururi picked Luna as his companion.

"It was a wild horse, but I tamed it. Luna has never kicked or bitten anybody, and is very friendly when surrounded by children."

He said he wished more people would donate books to his scheme. "Children here love comics and story books.

"Adults, on the other hand, need inspirational and how-to books, like how to farm, that kind of thing."

Sururi dreams of one day owning his own Kudapustaka horse - and a real library too.

"I hope I can have a small library in front of my house," he says. "But I know it is only a dream."