The third book is called "An Applied Guide to Water and Effluent Treatment Plant Design", and it is going to be written in the informal style of the first one. Once the spike of work is out of the way, I'm looking forward to enjoying writing is as much as I did the first one.
I'm really proud of the book I'm presently proof-reading, "Plant Layout". The more formal style and sheer size (1000 pages +) of the book have meant that there has been far more QA, rewriting and revising than there has been free-flowing writing, but the finished product is gorgeous, if I do say so myself. I have high hopes for it.