The Complete Musician, by Steven G. Laitz, was required for my undergraduate theory classes. It comes in one complete volume. There are two accompanying workbooks.
The writing is verbose; it's not concise. This has led to a lot of stopping, re-reading, and more re-reading to understand what the author is talking about. He could've used a course in writing efficiently. It was designed to be worked through from the beginning to end using the workbooks for more practice. The practice is vital to truly learning and understanding the material, like all skill-based activities.
The topics cover diatonic and chromatic theory with numerous examples. Being able to read a keyboard score is vital.
You will be able to understand harmonic analysis: i - v6 iv6 - V
as well as being able to write chord progressions.
If you are able to work from beginning to end, it may be worth your effort as you'll be able to see harmonic structures in the pieces you play from Bach to Beethoven to Chopin to Scriabin which may make memorizing their works much easier.