Most of it is good.
Well... More than it being a guide to critical thinking, it's soft version of the formalisms. The first seven chapters are really good and well written with simple illustrative examples. Eight is meh and then on it's painful. The so-called chapter on probability (Don't bet on it), that's exactly what it is; the next one is also bad. The last one is nice, regarding what to watch out for in debates and discussions, but it's overall presentation is lame. Take the few useful lines in chaps 8 & 9, a fair portion of 10 make it one chapter and you have a really good book. That's why Ive given it 4 and not 3 stars.
However, I must say, this is formalisms for the uninitiated. If you are looking for critical thinking, with a more problem solving and hands on approach, better try, Thinker's toolkit by Morgan Jones.