Fantasy: Boy rescued by swordsman, taken to a house in another dimension where he learns fighting/magic

[Chris]

There may be other dimensions that other characters can travel to, but I'm not 100% sure.

What I am sure of:

I read it in the past 5 years, but I'm not sure exactly when. I'm pretty certain it was a kindle book, possibly kindle unlimited. It's not in my book history, so it must have been free or unlimited, since those are the only way to not pay, I believe. I think it was also written in the past 5 years. It's geared towards adults, possibly young adult.

The swordsman that rescues the boy disappears for most of the book.
There's a pool in the house that heals the boy from his training injuries.
There's a room in the house full of dolls...that talk.
There's another room in the house that is a meadow (in which I believe they have to fight a swordsman for food).
There are these weird black cloth/shadow beings that also inhabit the house.

[Chris]

And this was solved...on Reddit. House of Blades, by Will Wight.