Main Question or Discussion Point
I'm not squeezing this into my degree (Physics), but I'd like to buy a good Logic textbook online or whatever. Thanks.
To some extent, yes it does. While logical truth is constant human understanding of it is not. For example, anything written before Russell will not include the revisions he made. In fact Aristotlean logic was still popular well into the nineteenth century.Does that really matter in logic?
What other textbooks would you recommend?
This book?What do you want to know about logic? Do you want to know various latin names for common argument forms? Do you want to learn a symbolic calculus for propositions and logical connectives? Do you want to learn about deep issues near the foundation of mathematics?
If want something substantial that covers a lot of ground in depth, then a reasonably heavyweight choice is Kleen 'Mathematical Logic.' If you just want to learn the propositional calculus and a fiew latin words, then just look at what textbook your local university uses for Symbolic logic or Reasoning courses. Choosing between these school books is like choosing an intro calculus book: just go with a cheap one.