Among their “deals of the day” Amazon (US store) is including 3 Kindle Edition Spider-man collections, each for just $3.99.
If you want to see how the Kindle Edition price compares to the hardcover or softcover price, here are some screenshots.
They are also much less expensive than on Comixology, which has them at $16.99, $10.99 and $10.99, respectively. And since you can now sync accounts, you can buy the Kindle Edition and still read it on the Comixology app.
I already own a paper copy of Spider-man: Blue, and it’s pretty good. If you liked Hulk: Grey or Daredevil: Yellow, chances are you’ll like this. And while I’m already subscribed to Marvel Unlimited, $3.99 seemed like too good a deal to pass up for the Masterworks Vol 1 collection, and Comixology has a better reading experience than Marvel Unlimited, so I went ahead and bought that one. Not sure about the 2014 series though.