I liked a large portion of the book and the idea that our resting state is happiness. I liked the organisation of the chapters and the way the book is broken down.
Some of the things I found frustrating:
The book seems to promise that it will provide and solve a happiness equation by means of maths and engineering. But the book in reality is a self help book that does not provide a formula but gives various strategies over numerous pages. There is a lot of mathematical and engineering language to justify the name and front cover but this often feels contrived and shoe-horned in.
The book tries to take a scientific tone but lacks references and research, it often feels like a long and elaborate opinion. This is still interesting but would be stronger if there were more links to the work of others.
The last chapter on intelligent design didn't really make sense to me, I felt it was oversimplified. He uses the analogy of a monkey randomly typing letters and how long it would take to create war and peace, in comparison to the evolution of creatures on earth. But there was never a single organism working alone, there were many, and thus the probability and speed of a single species was faster than he suggests in his model.