Thanks for the comment!
Yeah, I feel like for some reason Gaming treats UIs as some sort of unfortunate burden, and makes it a massive pain to implement. Unity's new USS system is a massive step forward, but it's still a bit complicated to get a handle on, and requires a LOT of work to make it fit in with other systems.
I was hesitant to make this free (it was quite a bit of work after all); but I think I'll leave it as is, unless I somehow start adding enough features to the point where I cannot justify the time for free. Though regardless, I plan on leaving the core version out there for free.
So... a serious book about the history of passenger rail in the USA?