Looking For A Book...

[shingo]

Good evening,
I was wondering if you might be able to help me out on this one. I am looking for a book which covers as much music/piano theory as possible. In my lessons I discuss the various elements of theory, but, especially for the more technical stuff (at least technical for me), such as cadences and modulations I would like to be able to read up on them afterwards and make sure I fully understand/don't forget.
I have done some looking around but I am not completely sure what the highest level of theory is, if there is one, so it is hard to see what each book covers as most tend to be a series of books instead of one.
If any textbooks cover all of this, could you perhaps point me in the direction of one as I assume many of you will study music either at college or at higher education.
Thank you for your time.

[keyofc]

Tonal Harmony by Kosta and Payne covers all of that in depth. (Textbook)

If you don't want to do that, and read something a little more conversational,
I suggest the Snell theory books,  (Piano theory fundamentals) there are 10.

I find Tonal Harmony hard to read - but know many people love it,
but I think the Snell theory books are the best I have found that are graded by level.

[shingo]

Thank you ever so much for your response, it is warmly welcomed. They are great suggestions, I will have a look at both.
Thanks again.