Where to buy
Paperbacks: May be ordered from your local bookshop, or online from most outlets, such as the Book Depository: https://www.bookdepository.com/Other-Mermaid-Billy-OShea/9788799642632?ref=grid-view&qid=1634386625163&sr=1-1
In Denmark, the paperbacks are on sale in the gift shop of the Round Tower of Copenhagen, and are also available from the bookshop Fantask.
Kindle: Available from Amazon
Audiobooks: Available from most audiobook distributors, including Mofibo, Audible, etc.