These books are practically the same! The only difference is that the 2nd edition has an additional practice test at the end, so if you are debating which one to get the 2nd edition is the way to go. However, if you already own the 1st edition, there is no real need to buy the second one.
We also have video explanations for most of the questions in both of the books. Check them out here:
And here you can find the explanations for the additional practice test in the 2nd edition :)
Hope that helps!