Evernote Essentials v4
For a limited time you can get Brett Kelly's excellent (and recently updated) book Evernote Essentials for half off - only $14.99 in the iBooks Store or in other formats directly from Brett.
I'm still on the fence on how much I want to use Evernote, but if you're at all into using Evernote this is a recommended book to pick up and learn more about a great app.
Screenshots from Evernote Essentials v4 permalink
Note: These are from the iBooks version on my iPhone 4.