My book Writing High-Performance .NET Code is already pretty inexpensive by programming book standards, but I’ve added a new deal. If you want to do get both the PDF and the EPUB, you can get 25% off the entire order, which basically makes one of them over 50% off.
Just go to http://www.writinghighperf.net/buy,
add both formats to your shopping cart, and use the 25PERCENT discount code at checkout to receive the discount.
Update: The discount code wasn’t working reliably, so I’ve just added a third buying option that is a bundle of the two formats.