Aprende gramática rápido y fácil

Aprende gramática rápido y fácil - Aída Calderón, Elizabeth Sayún Affordable, very well explained and to the point. This little book is a very useful aid for someone teaching Spanish grammar. The concepts are presented in a very comprehensive way, with examples to make the understanding even easier. The only thing that let me down a bit was that there was no section with the correct answer to the many exercises of the lessons so you can't be sure you got it right all the time.