I found Formal Logic easier to read from a textbook (I guess it wouldn't matter if it was an electronic one). I was actually an old book which my uncle had used during his college days.
from here
"The data for the study came from the PsycINFO database, which provides more than 3 million references to the psychological literature from the 1800s to the present, including peer-reviewed journal articles, book chapters or essays, and books."
Something's wrong, I think. 3 million references is a lot!