Thought I would change things up and finally turn "one day I will try some Manga" into a reality. Deciding where to start is difficult when you don't really have tastes to build on yet, but a few names came up repeatedly when I was looking at stuff so I grabbed 20th Century Boys by Naoki Urasawa, and two one and done volumes by Inio Asano: Nijigahara Holograph, & Solanin. I'm pretty sure Ty recommended Solanin ages ago so cheers for that. Not comic related I guess, but I haven't picked anything else up lately so that's all I've got.
Nijigahara is a love it or hate it piece, but Asano is still one of the best contemporaries out there. Solanin is just wonderful. I actually think 20th Century Boys has a lot of problems. It's fun, but it is totally undeserved how it's put up on a pedestal. If anything, Monster is likely Urasawa's best work. I heard some insider information from someone who was a manga assistant and worked in the industry that he actually had someone else writing most of his series up until now. Odd.
Anyway, manga! Let's start with something I think you'll like. You like horror, so read Uzumaki by Itou Junji. It's available in English. If you like that, I also suggest Fragments of Horror by him as well. I think my favorite works of his aren't translated still. Next, would be an epic fantasy adventure with lots of Horror inspiration, Berserk! Must read. If you read one manga, just read all of Berserk.
Important, great manga authors who you should experience: selected works. I'll select somewhat short pieces by great writers/artists available in English.
Osamu Tezuka - MW (Osamu Tezuka is called 漫画の神様 - The God of Manga - because he is the single most influential manga author of all time. He bounced around so many art styles and genres, and he's quite prolific.)
Matsumoto Taiyou - Gogo Monster, Tekkon Kinkreet, or Ping Pong
Tatsumi Yoshihiro - Abandon the Old in Tokyo or Goodbye
Taniguchi Jiro - A Distant Neighborhood
Hagio Moto - The Heart of Thomas
Hayashi Seiichi - Red Colored Elegy (this piece was hugely influential in Japan on all kinds of art)
Takehiko Inoue - Nothing short, sadly, but his three largest works are all very good and very famous. If you want a youth basketball manga taking place in high school with a flawed protag who really grows, read Slam Dunk. If you want a retelling of the life of the famous samurai Miyamoto Musashi, then read Vagabond (the art will blow you away). If you want to read about people who play wheelchair basketball, and their life problems, read Real.
Unfortunately, for one of my favorite artists in manga, I can't recommend a short manga. Eyeshield 21 (it's like super powered high school American football) or One Punch Man (maybe most accessible for a Westerner. Very funny with great action) are both incredibly fun and beautiful. Murata Yuusuke's art is phenomenal.
Lastly, since I failed in naming any female authors, let me point you to some of my favorite works.
Mori Kaoru's A Bride's Story is kinda slice of life about 19th century Central Asian nomadic tribes and several different women who get married and how their stories connect. The art floors me every time, and it's meticulously researched, so the people and their culture feel very real.
Arakawa Hiromu's Full Metal Alchemist is famous for a reason. It's a really great adventure. Besides the cute, deformed art sometimes used for comic relief (called chibi), I love pretty much everything about it.
Gotta promote Indie authors! My Lesbian Experience With Loneliness by Nagata Kabi is an autobiographical manga about a young, depressed virgin's experience exploring her sexuality and eventually seeking out a lesbian prostitute.
If you wanna read LGBT manga, Shimura Takako's Wandering Son is beautiful.
Sorry this post is such a mess. If you want me to go into detail on anything or you want me to find you specific recommendations tailored to your interests, I'd be happy to!