Building Language provides an introduction to Latin stems as the basis for much of the English and Spanish languages. Ten lessons introduce important Latin stems.
Leads up to the "Caesar's English" program for advanced elementary students (5-6?). This is more basic, with Latin roots suitable for grade 3-4 vocabulary study.
Can't give it a resounding thumbs up as too many pages felt like half of the (minimal) text was filler repetitive instructions... but it wasn't painful to do, and for beginning with Latin stem studies that's very important imo.
We won't be continuing with MCT's vocabulary books, though. I looked closely at Caesar's English 1 before we finished this one & decided it wasn't a good fit for us.