Alex asks another question:
You mention in the book that many of the final stops are not realeased. Are they “p”, “b”, “t”, “d” and “g” only? Also are they still not released in the plural form of words that ends in “s” e.g. “stops”?
Yes, those are the primary ones you need to worry about.
It’s particularly important not to release a stop sound when it’s followed by another consonant, even if it’s part of the same word, as the final S in the word “stops.” If you release the P before the S, then the word will sound something like “stopus.” A good example of that is the word “apartment.” Don’t release that middle T. Otherwise it will sound like “apartament.” Pay attention to these consonant clusters. The opposite error would be to skip that middle T completely and say “aparment.” This is actually a more common mistake and is often made by native speakers of Spanish, Portuguese and most Asian languages.