I agree with ttanaka. It's been a while since I have read the starting hands essay on the main page. But I can comment on what I think about KJ.

I have called half my stack with KJs before. So keep in mind that when playing in tournaments (as I usually do) it's all conditional. But as a general rule, for a beginner wondering how good KJ is. Here is my rules.

KJ suited and off from early position on a full table is a fold.
KJ suited is a raise from late position in an unraised pot.
KJ off is a limping hand from late position in an unraised pot.

And as I said before, but I want to re-stress. It is conditional. If you ask any poker question, the answer will most often be, "It depends." The same is true for how to play KJ. The rules I gave are very general.