The whole arrangement of every score is beautiful as in the game I recommend it 200%
Most of the songs sound really good and range in difficulty by a moderate amount, good for intermediate pianists. My only issue is that on some of the more difficult songs, some parts will just not be there, for example: in Death by Glamour, the first 1-4 measures of the song were written the exact same as the 5-8, but in the actually song, they add in some extra notes in the background (first 1-6 and 6-12 seconds if you want to compare it yourself). Otherwise, I do not have any other issues and definitely recommend.
The arrangements are a little more stripped down than I'd like for some piece like "Undertale", but overall this will be a lot of fun to read through. Great book for some sightreading practice as I try and I emerge from my low-intermediate cocoon. Notational schemes don't bother me as much, but I also think key signatures are more or less optional these days :P Thanks for making the music accessible!
Buyers BEWARE: If you know how to read music well, THIS IS NOT THE BOOK FOR YOU. The notation is terrible; there are no key signatures used. Every piece just adds a sharp or flat on EVERY note that it's needed. I was super excited to learn all the songs, but I cannot get over this notation. I got this book to get over learning from various free sources online where the notation had minor issues or wasn't accurate in places, but this is worse than that.
Sorry to hear this book wasn't a good fit for you! The UNDERTALE Complete Piano Score Book features simpler arrangements that are more suitable for beginners. The UNDERTALE Piano Collections (Volume 1: https://www.fangamer.com/products/undertale-piano-collections-volume-1 or Volume 2: https://www.fangamer.com/products/undertale-piano-collections-volume-2) features more complex arrangements that may be more suitable for your skill level.
It is very complete and beautiful