Reddit reviews Complete Taekwondo Poomsae: The Official Taegeuk, Palgwae and Black Belt Forms of Taekwondo

• As /u/tubbyx7 points out, Ik-Pil Kang's book is considered one of the definitive explanations of Kukkiwon-style poomsae. It's extremely precise and technical, to the point that tournament judges will use it as a reference. If you had only one book, this would be the one to have.
  
  Warning: you want the version of this book that includes both the color belt AND the black belt poomsae. There are other editions in which the two are broken into separate volumes.
  
  The book is out-of-print, but used copies are easy to find. This is the edition you want: https://www.amazon.com/Explanation-Official-Taekwondo-Poomsae-Korean-English/dp/899123724X/ref=sr_1_2?s=digital-text&ie=UTF8&qid=1497879640&sr=8-2
  
  
• Yes, there is a Kukkiwon textbook. I own a copy and refer to it sometimes. If you're building a library, it's a must-have, though in many ways it's not as useful as the above. It contains both English and Korean for every paragraph, though the English translation is not awesome.
  
  The most recently published edition is 2005. https://www.amazon.com/Kukkiwon-Taekwondo-Textbook-Korean-English/dp/8973367501/ref=sr_1_1?s=books&ie=UTF8&qid=1497879834&sr=1-1
  
  
• What I love about this book is that it's a good reference for all the Kukkiwon poomsae as well as the older Palgwae poomsae. I have referred to this book quite often:
  
  https://www.amazon.com/Complete-Taekwondo-Poomsae-Official-Taegeuk/dp/1880336928/ref=asap_bc?ie=UTF8
  
  
• I assume you already have a copy of "A Killing Art". Of course that's the go-to reference for historical information (though one could argue a fair amount of bias in its story).
  
  
• See also: http://taekwondo.wikia.com/wiki/Category:Book

Here's the link without the affiliate tag: https://www.amazon.com/gp/product/1880336928/