Not sure how this works as I don't have a Kindle, but saw that Derren posted about the discount on Instagram.
For those who don't know, Derren is a magician based in the UK who specialises mostly in hypnotism. Most famous recently for his Netflix specials 'The Push' and 'Sacrifice'.
That being said, this is a book about happiness with a lot of supporting evidence based in philosophy and psychology to the point where this is mainly a book about Stoicism.
Fantastic read. Highly recommended.