You know how these work. This offer is good until May 30, 2018 (if I did the math correctly):
From the web page:
Work hard, cosplay hard! Build your dream project with the Humble Book Bundle: Cosplay 2.0. Featuring guides from Mood Designer Fabrics, Adam Savage, Kamui Cosplay, Punished Props, and others, this bundle will give you more skills than you can shake a staff at.
$240 WORTH OF DIGITAL BOOKS
PAY WHAT YOU WANT
Have fun. (<- That part is from me)