These are all from the ITF side:
I believe that you can get Gen. Choi's 15 vol.
Encyclopedia of Taekwon-Do and the single volume version from
www.taekwondotimes.com (I have never seen any way to purchase individual volumes of the 15 volume set).
You should also check out
Taekwon-Do: A Guide to the Theories of Defensive Movement by Mark McCarthy and George R. Parluski. It's out of print but available on amazon.
Master Jim Hogan has two books that are worthwhile reads:
Effective Taekwon-Do Sparring and and
Taekwon-Do Patterns: From Beginner to Black Belt.
The best resource I have seen on patterns, bar none, is a DVD produced by Grand Master Choi, Jung Hwa (ITF Master Class DVD) available at:
http://www.treniconline.com/detail.asp?c_urn=183&show=allpgno2&urn=3108&pg=2 It covers the first 9 patterns in detail with GM Choi giving personal instruction on each pattern.
There is also a DVD series put out by the Japanese ITF that covers the patterns up to 3rd dan. You can purchase it here:
http://taekwondotimes.com/store/index.php?act=viewProd&productId=49
Lastly, there is the Legacy CD-Rom that was put out in 1997 that includes video of all 24 patterns, a scan of the first edition of the Encyclopedia, .wav clips of a lot of Korean terminology spoken by GM Choi, Jung Hwa and interviews with Gen. Choi which can be bought here:
https://ssl118.alentus.com/comdo/catalogue.aspx This includes ore materialthan the Master Class DVD, of course, but without the commentary on the patterns.
Hope this informaiton helps.
Pax,
Chris