Geeeez, this should have been adapted to anime ages ago! Now that Hakkenden has been, maybe someone will think to adapt Silver Diamond too, since they have more or less the same light 'shounen-ai' content (well, up to the point I'm at, at least, i.e. beginning of volume 9).
After the initial buildup--get past the first chapter or so, basically--it has a good pace, incredibly touching character development and relationships, a plot planned out extensively, considering numerous foreshadowing the author drops from the first few chapters on--for reveals to come dozens of chapters later--and an expansive fantasy alternate world with recurring secondary characters, let alone the main groups (she keeps track of every townsperson of every town she draws, I swear), and establishes its culture, creatures, and materials in detail.
Aside from the steadily strengthened friendships and bonds between Rakan, Chigusa, Narushige, Touji and those to appear later, there's another thing I love about it--I rarely find myself genuinely laughing aloud in non-screwball, slapstick comedy type of manga (such as Gintama, though there are less humor-oriented manga and anime out there that have gotten me laughing), but this manga left me chortling several times, which I hadn't expected at all when I began the series. I hadn't expected much, in fact, and am so glad I continued past the first few chapters.
One of the best things about it is that Rakan, despite the impression he might give in the first chapter (I thought he was a flowery sweet pretty boy type protagonist when I started), is actually really a levelheaded, determined, deadpan snarker, sometimes fiery type of main protagonists, which is much more alike to Shino from Hakkenden than what I'd expected on first look (which was Luka from Uso-something, who was...kind of weak-willed and foolish in my opinion, and part of the reason I never got around to continuing the series), while still very kind and sincere. His design subtly changes later on (even in the first volume) to reflect that, to be honest (at first he's drawn much shoujo princy kind of prettier, but that's reduced once he starts getting snarky and monotone at Chigusa's antics).
I liked the characters from the beginning, but by volume 7 and 8 they'd ensnared me in the way well-loved and familiar protagonists do, with me going "eeeeee" inside my head (and a little out loud) over every awesome or heartfelt move they made, and it'd deeply affect me if something even more painful--or tragic--than most of them had been left with happened to them. Nonetheless, the villains, too, are well developed, with dark depth in their hearts that's hard to see through. I still wonder what turned Kingen into what he is today, to cause such dire circumstance, and to do what he plans to do to the world. They leave me pissed a lot, though they aren't the only people covered in mystery--much of the cast is, still, by volume 8, whether it has to do with their origin, former life, or heritage.
The author obviously put a lot of heart into this, and I'm glad to see way more readers than I thought, since I'd seen the title several times and had not until today, when I decided to give it at least one chance, realized its fantasy action adventure drama mystery gloriousness until I got hooked. It especially came over me when I realized the fantasy counterpart world WOULD be explored at some point--however, at some point within volume 1 or 2, the characters come to mean too much to you for that to be as much of a concern until it becomes one.