The animals on the cover of Mastering the Lightning Network are Wood Ants (Formica Rufa).
Many of the animals on O'Reilly covers are endangered; all of them are important to the world. To learn more about how you can help, go to animals.oreilly.com.
The cover illustration is by Karen Montgomery, based on a black and white engraving from FILL IN CREDITS. The cover fonts are Gilroy Semibold and Guardian Sans. The text font is Adobe Minion Pro; the heading font is Adobe Myriad Condensed; and the code font is Dalton Maag's Ubuntu Mono.