Recommend a book on music theory(?)

I’m not actually sure that music theory is the term for what I’m looking for. I’ve been taking voice lessons for about a year and am getting to the point where I would like to learn more about the *structure *of songs. Stuff about chords, and scales, and how to change the key of a song, etc. Is that music theory? I’m not so much looking for terminology (legato, staccato, etc.) because my voice teacher goes over that with me; if it’s in the book, though, I’ll read it.

Any recommendations?