This probably should have gone in off-topic, as was suggested.

You should first tell us about your efforts to convert this pdf to txt.

Google the words pdf convert and txt

You will see a number of programs that do that. Try them and let us know the results.

I don't see why this won't work.

This looks like a great book, and I have read a more modern version that was even greater, but I forget the title. I think that Stanley was accused of not being completely reliable.

After you get it into txt (or html) form, FBreader would be the perfect way to read it.

Oh, the book I read was

Into Africa: The Epic Adventures of Stanley and Livingstone by Martin Dugard

It was great.

Edit: And while you're reading this kind of book, check out The White Nile and The Blue Nile, both by Alan Morehead. Also fantastic.