Okay, just had a look through this.
First off, I know nothing about Underland and I assume most readers here are in the same boat, so I appreciate that you introduced the setting and all the creatures within the story in a way that could be followed by people who are unfamiliar with it. The journal especially was very helpful, though you did neglect to put any kind of 'go back' link on any of the pages. There were places too where some simple scripting was badly needed, most glaringly right before the 'final confrontation' where you're having to tell the game what other characters you've got with you.
The writing itself was serviceable enough, though I did spot some typos, and structurally it started getting kind of sloppy and rushed toward the end. When Lizzie was captured by the Gnawers is when I would've expected things to get really interesting and complicated to expound on the whole 'horrors of hate' thing in the title, but instead it just rushed from there almost immediately to the final fight.
The setting was creative and imaginative, but I can't exactly pat you on the back for that when it's not your setting in the first place. What's left are the plot, pacing, writing style and characters; the setting helps shape the first, the second I already mentioned, and the latter two especially felt a little bland when that should've been the opportunity for the story to shine. Lizzie is a normal girl brought into this bizarre world, but everything is just described in this very straightforward and flatly emotionless way. She never actually seemed to think or react much to the things happening around her, and was basically forced into this extremely passive role and just got swept around by the story's events without the player having any say at all in the matter. Which sort of brings me to the other major issue of how completely linear the whole thing was. 'Ugh, I guess I don't have a choice' was practically the protag's catchphrase. Kind of problematic when writing a story in a format that's supposed to revolve around them.
Given a choice, for instance, I wouldn't have necessarily chosen to have the main character immediately turn on the friendly, helpful humans who had just saved her and her brother and were living in a beautiful city in peaceful partnership with cool giant bats, just because some violent furries who had kidnapped them and were talking about torture and eating people alive were now going 'from my point of view, the Underlanders are evil'. The oath with Silver was kind of out of nowhere too seeing how they were literally pledging to die for each other when they had just known each other a couple of days (at most...little fuzzy on the timeline there because that whole segment is one the story just flies through) and hadn't met under the greatest of circumstances. But both of those really just go back to pacing again. There are segments of the story that really need to be expanded or made into actual choices about how the protag feels about all this to make it have the kind of impact you want, and there's certainly plenty of room for scattering a few more links around to do just that.
That said, the only reason I've bothered to go into this kind of detail in the first place is because I think this has a lot of potential. It's a decent enough story now but with a few tweaks and some fleshing out could be something more memorable. It's done enough, anyway, to make me think about reading up on the series it's based on sometimes, which is more than most fanfic around here manages. :)
