We recently bought a piano and I want to teach my DS7 how to play (I play but am a little rusty since I haven't owned a piano as an adult). He already grasps a lot of the technical things about music but hasn't had the chance to apply them because we haven't had an instrument. After previewing a few different books on Amazon, I think they may move a little slow for him. Any recommendations on a beginning piano book for gifted kids?

I recommend that you start with elementary aged books even though your child may be gifted. Even if his sight reading, ear training and theory are excellent, there are a lot of things in piano playing that take time - the finger position, hand-eye coordination, posture and just all of it coming together. If you jump in at a higher level or use an accelerated course, all of these things may or may not fall into place for a child. If after you start teaching a course at the beginner elementary level and feel that your DS is getting it all and needs no repetition to advance, you have several options:
1. Condense that level to accelerate to the next level
2. Jump to the Accelerated Piano course of that publisher
3. Use option #1 but add in more repertoire to include various artists and styles of music
From the little experience that I have, Faber's Piano Adventures series and The Music Tree series are pretty good. We use the Faber PA series now after graduating from preK level Alfred, JT and Little Mozarts. I love how Faber has supplementary books like the Developing Artist series, Gold performance books and the "PreTime to BigTime" series. They also have an "Accelerated Piano Adventures" which might be an option you can pursue if you find PA too slow for your child.
I also add in really fun, interest driven music books that boys my son's age like (he is 6) - e.g. Harry Potter, Star Wars, Pirates etc in addition to Mozart, Beethoven etc.
We have a teacher who is happy to teach "extra requests" and flexible enough to fit these into her curriculum.

Good luck.

The Royal Conservatory of Music books from Canada are lovely and make significant advances in terms of difficulty at each level. The repertoire is varied and rich.

My impression is that the books are all arranged in similar orders in terms of what basic knowledge and skills are introduced, but you can move at any pace that works for your kid. Each of my kids stayed on the basic method books for a very short period of time. I remember my DD8 (when she started piano at 5.5 yo) spent 2-3 months with a few method books that would usually take at least a year to cover, and then just moved on to standard repertoire. Even when she was using these method books the teacher supplemented with lots of other pieces as well. My feeling is that the books don't matter as much as the experience of the teacher who can tell what is the right content and pace for a kid.

In terms of books, I agree with aquinas that the RCM books are really good. But they are not method books, they are leveled repertoire books (meaning that they don't explain note names, time values, key signatures, expressions, etc). In terms of method books, aside from what has been mentioned above, we also liked very much Succeeding at the Piano by Helen Marlais.

DS5 is using Bastien books. He cruised through the first few fairly quickly compared to a friend that started a few months earlier but there is theory along the way which is great. I also find free sheet music of favourite classical songs, Star Wars etc and he makes his own music up too.

You can look at the Suzuki books. I love them mostly because they get into playing actual pieces with both hands quickly. DS5 has been having lessons for about 6 months now and absolutely loves it!

Playandlearn is right. I enjoyed this book for music theory:

http://www.amazon.ca/gp/aw/d/1554400112

We started with a combo of Faber and Suzuki, which worked well. We've moved on after a little less than 2 years to just playing music from intermediate books. The combo was a great start, but more important was switching to a professional musician from a piano teacher. We travel an hour twice month and I manage things in between.

Bean

the music tree is a great book for beginners. in general, i wouldn't jump into more advanced stuff, without some focus on the basics, because a lot of piano is repetition and muscle memory as well as the theory and understanding...but if your DS grasps concepts quickly, you can simply move through the material at a faster pace, but the repetition is a necessary component in the process.

i'm personally not a fan of the suzuki method, because it puts zero emphasis on musicality, and so, kids usually end up playing the notes by rote, having little to no artistry in their actual playing. ends up sounding robotic, imo. of course, this is coming from someone with a degree in music (aka, a bit of a music snob ), so this may not apply to/bother you.

Suzuki bothered us (dd especially) but she had started out as a four year old with a violin, so it was an easy transition. The Faber almost over does the dynamics, so it sort of evened out.

Dd did not want to continue the combo- she wanted real music. In retrospect, I would consider looking at Faber's "older beginner" series. I think it moves through the basics more quickly.

Our teacher likes Alfred books. There are many levels and they come in sets emphasizing particular aspects like technique (technic is the spelling they have in the titles for some reason unknown to me) , theory, etc.

Ditto-- DD learned all the way through the Alfred series before moving on to technique work with classic composers (Concone, Hanon, Czerny, etc.) and original keyboard masterworks (Bach, Scarlatti, Mozart, and so on).

I am resurrecting this old thread since I found a series that might work well for beginners:

http://fundamentalkeys.com/piano-method/

This is pretty close to how I learned piano as a child and until I decided I didn't want to practice anymore, I was doing pretty well.

The author is revising it and the new edition would be expanded but until then, the original edition is available and it is on sale.