I don’t read a lot of gay lit (that’s what fanfic is for) but I did pick up The Scottish Boy second hand and was impressed by the story and well-written sex scenes. There’s also black and white illustrations for each chapter.

Story is set in England in the 1300s. A knight who wants to prove himself ends up in charge of a rough, aggressive Scottish prisoner. It has a historic setting, battles, political intrigue and steamy sex, so I highly recommend it.

https://www.goodreads.com/book/show/50169793-the-scottish-boy

(Pic was done to promote the book)