@Liber-Monstrorum How did I get into reading BL manga? Pull up a chair - this will take a while to answer. ;-)
Seriously, I'm much older than most people on this site, so I actually began with reading slash fan fiction when I was younger. Slash (named for the slash in K/S, or Kirk/Spock Star Trek fan fiction) was the precursor to m/m romance in the U.S. After being a slash fan, and before I started reading and writing m/m romance, I got into yaoi and BL anime/manga when I became an anime fan in 2005.
I agree with you that BL manga is best when there's a strong story and beautiful art, especially if the character designs are beautiful. I think the strongest story I've ever read in BL manga is Shungiku Nakamura's Hybrid Child. It's moving and haunting - very powerful.