Theres a whole lot to like about this well-conceived and inexpensive math program. The main features of this program, according to author Maria Miller, are:

Focus is on conceptual understanding rather than rote problem-solving
Teacher instructions are right in the book; no need to buy a separate teacher book
Clear explanations are written for the student, so the lessons are virtually self-teaching
Lessons use lots of visual and pattern exercises
Mastery oriented:concentrates on each topic for a long time studying fewer topics per grade than with spiral
Emphasis is on mental math and number sense
Very little teacher preparation is required
Content aligned to Common Core Standards