11$ im not that cheap lol
Sorry! You said free, so I took you literally. Hey, I don't even know if you're ten and live off an allowance! Misunderstanding
Other books, well, that depends on how fast you're planning on advancing! If you're into scales and the like, "The Brown Scale Book" published by Frederick Harris Music has them all in it. It's a little overwhelming at once though. There is a series of books by the same company that breaks it up. The first is orange and called book 1, Technical Requirements for piano
A REALLY good book for learning notes by the same pubisher again is book 1, Four Star sight reading and ear tests, daily exercises for piano students, by Boris Berlin. It's orange, too. It's really good if you're teaching yourself. It has a 3 minute exercise for each day, with 4 bars of music where you name the notes and a rhythm to clap. I'd definitely get this one, if I were you.
The book I'd get after the Michael Aaron book would be the introductory album from the New Piano Series (same publisher as others). It depends on how much you want to purchase up front. Hope this helps!