More than 10 years ago, social studies teacher Edmund Lim, 43, realised there were no books documenting Singapore's presidents.

This month, three children's books on Singapore's former presidents are finally out in bookstores.

Targeted at secondary students, the books, written by Mr Lim, shed light on the country's first three presidents: Mr Yusof Ishak, Dr Benjamin Sheares and Mr Devan Nair.

Mr Lim said: "The younger generation does not know much about the leaders of Singapore, and much less about our presidents. The books cover lesser-known facts about them, document their everyday struggles, and would inspire many."

All three books in the series include facts on the presidency, such as how the president is chosen and what his or her duties entail.

Mr Lim, who also wrote Where's Grandma?, which won the Hedwig Anuar Children's Book Award in 2013, added: "I hope these books can help interest, inspire and inform Singaporeans. It is my little contribution to education and nation building."

To make the books more interactive and exciting for young readers, the Straits Times Press has, for the first time, teamed up with a Singapore-headquartered company that runs an app called SnapLearn.

By making use of the app's augmented reality function, readers can access additional digital material such as photos and videos. Users can download the free app on their mobile phones.

The books cost $10 each.

Books on former presidents Wee Kim Wee, Ong Teng Cheong and S R Nathan are expected to be ready by March next year.