all of them. Read, view, and devoure all them. None are gospel. All have great points.
The big surprise for me last year was Girls at play. It has great stuff in it though a bit touchy feely in between.
Liquid skills/Ken Whiting videos are probably the most watchable. - Soar, playboating and the books are good too.
Ej has some neat ideas and drills in all three of his videos and they are supported by his two books. The videos are more current.
Kent Fords rolling video is great and though a bit dated as far as general technique still excellent is his general paddling video. I found the books not as informative as the videos. Retendo though full of god basics doesn't really hold a candle to;iquid skills.
Kayak by william nealy is dated but fun read with some very interesting ideas about reading water.
Whitewater self defense is best viewed small pieces at a time but has good mellow dramatic info in it.
If you really want a mind blower that is kind of like a kayaking thrift store see if you can find "essential boat control". Tommy has thought way to much about boating but has some truly alternative ideas about how your boat moves. You just have to sort through everything to find the gem.
My point is that any one who has put out a book or video has thought about paddling a great deal and can bring some new idea to your paddling.
friend of the fork, knife, and spoon