Galina Kovalyova, the Russian national research co-ordinator for the PIRLS international study of reading, credits a tradition of home education and a strong literary culture for children's reading success and enthusiasm.
Analysis shows that on average 90 per cent of Russian parents play an active part in reading, writing, singing and telling fairy tales to children.
The climate may also have helped create a strong literary tradition, Dr Kovalyova adds: "Nordic countries that share Russia's long winter evenings also have home reading traditions." Russia's wealth of vivid fairy tales - most with a strong moral - help make reading a pleasure for children, she says.
Weak points in Russian children's reading progress include a lack of attention in schools to higher-order skills, such as literary criticism.
This could, she suggests, be a legacy of communism, which discouraged critical, independent thinking. "Children often do not express their own opinion and have difficulty combining information from different parts of a story or making an evaluation of the text," she says.
Bulgarian Dr Georgi Bishkov, a literacy expert at Sofia University, attributes his country's high rating in attainment and enthusiasm to a strong home reading tradition and long-developed reading diagnostic tools.
Teachers use personal reading plans for each child. Bulgarians are aware of their international standing in literacy and pride in this helps support teaching excellence at home and school, despite the economic difficulties of recent years, he says.