I have read janice kims learn to play go 1st vol. What do I read next? [besides her other books]

You may enjoy The Second Book of Go by Richard Bozulich.

Are you saying aside from her other books because it's a given that you are going to read them, or because you don't plan to read them for some reason? If you're not continuing with them for whatever reason and want another beginners book, then I'll recommend Iwamoto's 'Go for Beginners'.

If you are planning to read the other Janice Kim books then I'll second Ed's suggestion for the second book of go. I think that book could stay useful for a fair while. I think I should go back and read the chapters about capturing races, actually...

Also- Graded go problems for beginners. Reading strength is so important, so start practicing as soon as possible!

How cliche, have him read "The Second Book of Go" for his second go book...

Well, I also agree.

It is a great read and will still be useful until about the single-digit kyu level. Even then, reviewing the concepts in it isn't bad. Just last week I was reading some from that book, actually...

_________________
"You have to walk before you can run. Black 1 was a walking move.
I blushed inwardly to recall the ignorant thoughts that had gone through
my mind before, when I had not realized the true worth of Black 1."
-Kageyama Toshiro on proper moves

If you have already read Kim's Vol. 1, then I highly recommend Vol. 2 (Way of the Moving Horse) at least. It really opened my eyes to concepts of shape and the relationship between stones on the board. It reduced the overwhelming feeling of not knowing where to play, and provided a basic framework for the game.

In addition, I would second the recommendation for Graded Go Problems for Beginners. I think, as a beginner, even if you read just Vol. 1-2 of Janice Kim's series and worked through Vol. 1 of Graded Go Problems, you'd be on your way to success.

A good answer depends on what you have or have not learnt. KGS 20k is an ambiguous rank. Maybe you should just play, maybe read also alternative beginner books, maybe read books just beyond absolute beginner level, maybe books for improving your reading.