Because the book is a collector's item, it appears on:

In the vast ocean of Spanish regional literature, certain titles transcend their modest print runs to achieve a near-mythical status. One such book that has generated significant whispers in literary circles, on social media forums, and among collectors of modern Balearic narratives is (Dear Mallorcans).

These are the historic publishers of Riera’s work. Check their official websites. They occasionally offer direct DRM-free PDF sales for educational purposes.