If you are a serious VISUAL BASIC programmer and you want to make the jump to client-side web programming, you need to study this book.
Just in the area of functions alone, you will never understand how functions in JavaScript differ from functions in VB (e.g functions as a first-class data type, function literals, etc.) by just reading tutorials or looking at code here and there.
You won't understand these things, unless you have David Flanagan explain it to you.