heresy

If anyone gives you a free copy of this book Ten Commandments Twice Removed you should throw it away or destroy it.

Its deceptions are wrecking havoc within orthodox and specifically Evangelical Christianity.

why is so awful?

While it may seem subtly convincing, it denies core tenants of historic, orthodox Christianity [see Paul's arguments all throughout the book of Galatians] AND it is written and distributed by a member of a cult whose founder was a false prophetess [whose teachings included that non-Caucasian people are the result of relations between man and animals!]

for more on this cult's odd history and beliefs, check out the video on this page:
video

and see this page for their errors regarding Sunday and the Sabbath:
Sabbath or Sunday

Beyond this, it's author (who claims that the 10 commandments are a requirement for salvation) has broken them recently.
He divorced his wife (with no evidence of Biblical grounds) and has remarried - which according to his theology - is adultery.