I love these books. The first two are shorter and a nice prep for algebra. The algebra courses and beyond can stand alone for HS math. We use MUS because my kids need A LOT of repetition to make it stick. If you child gets math quickly or becomes bored easily then the first two books may not need supplementation before moving on to algebra.

That said, they are really funny books. My kids loved them. I will use their algebra after they finish Zeta in MUS.