On Page 41 under the section "How it works" the sentence is: After clicking the button, the program calls the btnAdd_Click event handler and the program execution starts at the top and works its way down, one line at a time, to the bottom...

Is it supposed to be btnAdd.Click or btnAdd_Click ? I should probably continue reading (and I will) but It's killing me to know right now

It is not a Typo. BtnAdd_Click() Refers to the Subroutiene Called by cllicking the "Add" Button AKA btnAdd.
When you double-Click the "Add" Button in the Desigh View. you will be directed to the Code Window. The Sub btnAdd_Click() Will Be built for you . then you need to add your useful code to it.

if you come from VB6, LIke I did you you might be interested to know that in order to call the code btnAdd_Click() From Another button, the sytax has changed to Me.btnAdd.PerformClick()