What's up, guys? If you haven't read House of Hades yet (or haven't gotten to what is probably the most polarizing point in the book, about two hundred pages in or so), you may not want to read this.
So, a lot of you seem to be unhappy with a certain revelation about Nico. You seem to be angry at Riordan, at Nico's character, at the whole situation as if it has completely ruined the series forever and nothing will ever be the same. "It never happened", you say, "Nico and Jason never went to visit Cupid. Nope, it's not true. And it's especially not true that we found out something about Nico's sexual orientation there, because of COURSE Nico's straight! He's a major character, he can't be g-g-homosexual!"
To all of you, I say the following:
Nico hasn't changed.
I'll say it again: Nico hasn't changed.
This revelation is simply that: a revelation. It's kind of a post-event plot twist for the latter few books in the first series, but it doesn't inherently change anything about him. His motivations haven't really changed, except that he's now afraid he'll be outed by Jason to the rest of the group. You can look back at his character and see that, yes, maybe those tortured expressions and that hatred of Annabeth make more sense, but that doesn't change any of his actions. He's not suddenly jumping around in a frilly pink leotard and batting sparkling eyelids at Percy.
His reason for saving Percy from Hades' prison, for helping the Demigods against Kronos, and for not telling the others about Camp Jupiter are the same. Nico is the same, sensitive person he's always been, wears the same drab clothes and gloomy expression that he always has, and has the same badass Stygian iron sword he's always had. He's going to continue to interact with Percy the same way that he always did (which, if you'll remember, has always included a lot of angst and guilt and drama). Until Percy finds out that Nico likes him and not Annabeth, nothing in their relationship will change one way or another.
The only reason you are so angry is because you're afraid that Nico's entire existence is now going to be to push the acceptance of homosexuality onto us impressionable readers. After all, it's a hot-button issue right now.
What if I told you that homosexuality has been around for pretty much ever? We even met the West Wind and explored his backstory of manlove. Having a gay character in a story about the Greek and Roman gods won't banalize it. It might make it a little more true to the original.
You're angry that Nico's going to change now. Guess what? I'm here to tell you that he'll stay the same. It just gives us another lens through which to view his character.
And that's never a bad thing.