This digital copy was obviously optically scanned from paper. It was done pretty well, but wasn't edited afterward. You'll see words like "stem" when the original text is "stern". There are other similar mistakes that could have been corrected. Slightly annoying but not enough that you'd give up on it.
Also, there are some grammatical errors of the form, "Smith brought it to Jones and MYSELF."
So, in general, an interesting book that could have been edited better in the original and in the digital copy.