Recommend a page turner for a history nerd getting back into reading fiction

I am getting back into reading fiction after having no time, focus or energy for years due to grad school, life, etc. I was a voracious reader through my teen years and would burn through novels but I no longer have the focus and free time that I used to. I miss it terribly!

I don't have a tremendously specific request but I do have some preferences that might help folks recommend something:

Engaging, not a slow burn. Something that will have me invested within 50 pages!

I love historical fiction, but prefer books rooted in historical accuracy so I'm a bit picky. I would love a well researched book set in medieval Europe or WW1/WW2, though not necessarily only looking for books within this genre.

I want to like and care about the characters! Again, I want to feel invested from the start.

Nothing with a devastating ending. I am a mental health therapist who primarily works with trauma looking for a bit of an escape and while I'm not necessarily looking for something light, I'd rather not be crushed to bits by the novel I'm reading.

Something with competent prose. Nothing that reads like YA fiction. I say this because I was recently recommended the ACOTAR series by someone who doesn't know me very well and this is the antithesis of what I am looking for in this regard.

Thank you!