What is a good way to learn how to read sheet music if you can play by ear?

I can read notes and play the piano by ear. I am playing elton john songs bc i have good natural rhythm and can read the notes. However, if you were to give me a song that I've never heard before I would have a hard time reading the sheet music. I know what the notes are but the tough part is getting the beat down. I can't afford a teacher. What is a good way to start practicing this? Are there any good books you could recommend?