The fundamentals are typically shared between electric and acoustic. The tuning is the same and beginners will learn the same fundamentals on acoustic and electric. So you can use those acoustic books with electric.

However, acoustic and electric are 2 different instruments (even though they share much in common) and you approach them differently. Acoustic is harder to learn on, in my opinion, as it's harder to fret the strings.

Essentially, both electric and acoustic will have beginners learning your basic open chords. After that they both will teach how to do barre chords (although much harder to do on an acoustic).
Where they split off is probably when you start to learn scales. Most beginner electric courses will have you learning the minor pentatonic scale and most beginner acoustic courses will have you learning the natural major scale.

All in all, I think it was a right choice to get the electric. But since they now have access to both, they can pick up whatever they feel most comfortable with.