The first outdoor library will open in Ljubljana's Tivoli Park, one of eight locations in the Slovenian capital and arguably the most popular such venue in the country.
Another popular spot is on Ljubljana Castle, one of the main tourist attractions in the city, where the selection of books is tailored to foreigners, who make up the bulk of the castle visitors.
The project, called Library under the Canopy, was started twelve years ago by Divja misel, a non-profit promoting sustainable living and sustainable development.
It has since spread to 13 cities and towns in Slovenia, and even Topolo, a tiny village just across the border in Italy.
The outdoor library sites often feature musical performances and readings, according to the main promoter of the project, Tina Popovič. Some sites have taken on a life of their own.
In Polhov Gradec, a small town outside Ljubljana, it took several years before the library took off but now it also features an ice cream and library stand and has "breathed life" into the local part, according to Popovič.
Some of the outdoor libraries will be open throughout the summer, others are installed just for a few weeks to accompany local events or festivals.
This year they will be available in Ljubljana, Polhov Gradec, Kanal ob Soči, Mala planina, Nova Gorica, Polšnik, Ribnica, Kranj, Novo mesto, Zagorje ob Savi, Bled, Ptuj and Vrhnika.