TOR says: This looks like a great foundation for understanding federal gun laws. If something isn't completely clear cut it is probably worth contacting the ATF (gasp, did that just come out of my mouth?) to be sure. I know things can get awful confusing; especially when it comes to imported weapons and required amounts of US made parts.
As always YMMV when it comes to the accuracy of this book. The author of the book will not go to federal (pound you in the ass) prison if he is mistaken, you will. Two points to whoever gets the movie reference.