Thanks a heap for bringing this set of books (Lessons in Electronics by Tony R Kuphaldt) to my attention!
The labs are much easier to follow and all books are 'free open source for downloading'.
I seem to remember that Tony was a proponent of what is called electron current convention.
That is he counted current as flowing from negative to positive.
This was a fashion around the time he wrote that book.
Most folks continued with the older conventional current convention where the direction of current flow is taken as from positive to negative.
Consequently many of the equations Tony offers have a negative sign in some places, compared to the same equation in conventional current textbooks.
All you need to do is use one system or the other consistently and not pick equations from each in any working you do.