Difference between Level I Secret Sauce and Book Zero?

Both seem to review the key concepts of Level I, so what are the differences? Is it worth reviewing Level I Secret Sauce before the Level II exam to brush up on Level I concepts, or is everything that is needed (and more) in the Book zero? I know it’s early but just wondering. Thanks.

what is book zero?

Book zero and secret sauce level 1 do seem very similiar. Honestly you may not need to read either. Just start reading for level2, and you’ll see you remember alot more than you think. If you dont remember something, then go look back

book 0 is about half the size of secret sauce

Book zero is the stuff from level I that you need to know for level 2. Secret sauce is all the important stuff from level 2.