So book 4. This one is all about why reactions happen. Why do some things when you mix them together react, some require heating, and some just never bother.
It has the potential to be a very boring book, as it discussing a lot of stuff about entropy, enthalpy and Gibbs free energy.
There are a number of videos that accompany the book and help bring it to life a little. Some of the chemical equations and calculations I find a little confusing, especially around metal ions. The crown ether stuff is also a little esoteric I found, but in the end with a bit of practice its possible to make some sense of the calculations.
Its quite interesting to see that given all this detail you can make some predictions about what reactions are possible and which aren't.
However all thats said there is a lot of equation manipulation in this bit - all relatively simple but there are enough steps that its really easy to miss off a coefficient here, or a plus sign there.
The book wraps up with a case study on batteries which is quite interesting. Going into the details of dry cells, NiCd and so on giving the design decisions around each.