I LOVE MANGA! And anime, too, but seeing as I am more of a reader than a TV watcher, manga came first. If I like a manga series enough, I will eventually break down and buy the anime for it (if it exists), although in some cases I actually got into the anime first and then had to wait for the manga to make it over to the US. And yes, I am one of the few people who shells out an ungodly amount of monies on manga and anime DVDs (I try to buy boxed sets whenever possible). This is because I only have (limited) internet access at work, so cannot DL anything.
I'm pretty picky about what I like to read, and for the most part, I tend to gravitate towards shonen series, because they have less frilly clothes, less annoying female characters, and more of an interesting plot. Below are some of the series that I have thoroughly enjoyed; for those of you looking for recommendations, I've included a brief description and the publication status.
= Trigun - totally awesome series, set on a desert planet. Like a sci-fi western, only with bigger (and weirder, lol) guns. This was one where the anime made it over well in advance of the manga, which consists of the two-volume series Trigun and the 13-volume continuation (12 so far, #13 won't be out until Dec.) Trigun Maximum. It has a nice mix of goofiness amongst the more serious themes, but it gets a bit angsty towards the end. All in all, though, this is one of my most favorite series and definitely one I would recommend.
= Saiyuki/Saiyuki Reload - this one is right up there with Trigun as one of my top favorites. It is impossible for me to adequately describe it, but trust me, it is DEFINITELY worth checking out. Great art style, and the story is not only interesting, but also the interplay between the main characters is HILARIOUS. However, I feel compelled to warn those who are under 18 that there is a great deal of swearing and violence so if you (or your parents) object to that sort of thing, then perhaps this isn't your cup of tea. Saiyuki is complete at 9 volumes, and Saiyuki Reload is currently at vol. 8 with more to come.
= One Piece - weird art style, but it grows on you. Plus, it is about PIRATES! Awesomeness and hilarity abounds. Vol. 18 just recently came out - however, this is one of those series that looks like it will continue for a LOOOOONNNG time, so there will be many more manga to come.
= Trinity Blood - another one with adult (notice I didn't say 'grown-up' lol) main characters, and also where the anime came out first - GORGEOUS animation, btw, I highly recommend it. It has vampires and the Vatican, and vampires working FOR the Vatican - fun times! The only downside is that the author of the book series upon which both the manga and the anime were based died a year or so ago. However, the anime series is complete (as far as I know), and the manga is currently at vol. 6 with more to come.
= Tsubasa - this is a crossover with another series, xxxHOLIC; both done by CLAMP, a fairly well-known group of manga artists. If you have read other series by CLAMP, you'll recognize some of the characters, but other than their names, there is no real connection plot-wise to their previous works. Both series can be read on their own, as the storylines don't so much overlap as briefly reconnect at various intervals, but reading them together gives a little more depth to each one. Each manga also has a helpful section at the end that explains some of the terminology used, as well as explanations of cultural references that us non-Japanese might not understand otherwise. There were quite a few that I didn't know, which cleared up things I'd read/seen in other series, so don't just skip the back section, it is worth reading! I'm not current on how far each one is atm (at one point, I ran out of money, and haven't been able to afford to go back and purchase all the ones that were published in the meantime yet), but I think Tsubasa is somewhere around the mid-20s and xxxHOLIC around #19 or so.
= D. Grayman - an odd series, but very well-drawn and funny. These aren't your average, garden-variety exorcists. But then, akuma aren't exactly your average, garden-variety ghost, either. And how can "innocence" be a weapon? <wry grin> The manga is currently on vol. 9, and I believe there is going to be an animated version coming to the US at some point, if it isn't here already.
Several people have already mentioned these, but they are also ones I like:
= Death Note
= Rurouni Kenshin
= Inu Yasha
= Ranma 1/2 (done by the same artist who does Inu Yasha - less plot, more crack)
= Fullmetal Alchemist
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