It's only available in the US, and it's on the proprietary platform Kobo, but once you have them it is easy enough to strip the DRM legally to migrate to the reader of your choice
not available in the UK unfortunately.. i saw it saying "bundles you might like" when i was on the site earlier and it said "not available in your area" which is weird, considering he is an english author lol
Just noting here: kobo ereader software has devotees, who are masochists. Itβs a deeply problematic and poorly designed software, especially with footnotes. And these are locked to Kobo. They can be read on anything that can run the Kobo app, but it will not behave like Books/Nook/Kindle.