The fourth one went over the subtext line to the extent where Rachel's "I am Straighty McStraight" would read as ludicrous denial. I am looking forward to seeing how that's handled in the fifth book.

I'd still love to read books besides my own which deal with it.

Oh, me too! KH's books are the closest I've found yet to genre fiction with a bi, poly viewpoint character. Rachel's not there yet, but after book 4, it's a place she could believably go, I think.