Not sure where this discount is coming from but I figured I would share it with you. You can pick up the vSphere 4.1 HA and DRS Tech Deepdive for $ 17.96 on Amazon.com. That is about as cheap as it can ever get in my opinion. Pick it up.
By the way, Frank and I are working on a major Update of the book. If you spotted any glitches or have any comments drop ’em here so we can incorporate them. Before you ask, yes we will be reconsidering an ebook version!