The thing that got me was because they said those two sound ones were different but my Korean friends said they aren't. He said if you listen closely they are the same but the other sounds change them so never focus on perfecting a certain sound because it will mess you up! My head was so messed up I cried. Kpop, LOTS of Kpop and kdramas helped me listen to the sounds. Lol
I have that book and got half way through and it confused the crap out of me. They are releasing a second one around Christmas time but the Japanese from zero is the best! I am on my third book. First was hiragana the second is katakana and the third is kanji. I will restart my Korean at some point but my Korean friends had to help me with parts of it like d/t, p/b, j/ch and k/g. Once I got that I was good.