If you took piano lessons as a child, or if you have a child who is taking them now, then you'll want to read Note by Note: A Celebration of the Piano Lesson by Tricia Tunstall (Simon and Schuster, 2008). I like Tunstall's description of music lessons: "weekly session[s] alone together, physically proximate, concentrating on the transfer of a skill that is complicated and difficult, often frustrating and frequently tedious, but that every now and then open suddenly and without warning into joy" (3). And the chapter on recitals is particularly, sometimes painfully, well-observed.
Recommended at Read Roger (see the comments for what readers remember from past piano lessons; Spinning Song, anyone?). I only wish there were something comparable for violin lessons--that's what Leo takes. Although Little Rat Makes Music by Monika Bang-Campbell (illustrated by Molly Bang; Harcourt, 2007) comes close, from a child's perspective. So that's what elementary violin playing looks like!