The episode is roughly the same size as the ones before. I think you've missed out a couple of things. There's a threesome with Céline and Lilly and a sex scene with Eva. There are some problems with getting that last scene, for players on a certain route. That issue will be fixed in the next update.

Players on Eva's path who cleared the simulation in a previous episode, are unable to get the conversation option to get Eva to join the harem. This happens after the lewdness on the ship and is a conversation in the ruins later on. If ep015_eva_truth is False and ep015_eva_love is True, you likely didn't get the harem option in your playthrough of Episode 18. You can check the state of these variables by pressing Shift + O top open the Developer Console and typing the name of the variable, it should return its value.

I'll remedy this problem in a future update, but for now a workaround would be to set a variable via the Developer Console. You activate the console by pressing Shift + O just before the conversation menu for the ruins comes up, then you type the following: ep015_eva_truth = True

After that Eva's option should be available. This will of course be fixed in the next release.

Yes, once it's finished, around Episode 24.