Don't take too much from my three-star rating, as I haven't read the book in earnest, only a few chapters.
But I'm sure you'll appreciate my clarifying this: this is an intermediate-level economics text, not a general survey text to be used by college freshman. It is for second- or third-year economics majors, and while students don't have to know calculus to get through it, they'll certainly going to need loads of algebra.
Having said that, for an intermediate level text, it seems to be a bit on the easy side, on the level of, say, Mankiw's "Macroeconomics," now in its 5th edition. (At least going by the exercises I worked in four of its chapters.)
For something a little more strenuous, I would suggest either Froyen's "Macroeconomics" or Blanchard's "Macroeconomics."
Again, this is a specialist book for econ majors, and certainly not for high-schoolers!