When the Japanese "Star Wars" manga was released in the US by Dark Horse, the original cover art (done by the artist who did the manga adaptation, Hisao Tamiaki) was replaced with art done by an American artist Adam Warren.
I have never really liked Warren's work. And there is no better example of why than the cover of "A New Hope", on which he makes Princess Leia look like someone stapled a Zodiac to her face in place of her lips:
The lips are wrong, the noses are too big, and overall I just don't like it. (I suppose I should be glad that he couldn't make any changes to Darth Vader....)
It's an example of why "manga style" does not mean "manga"; Adam Warren is a "hot artist" because he is very good at imitation, but he is not drawing manga the way the Japanese do. What he is doing is drawing American comics in a manga style. The cover art doesn't even try to look like the art inside, which is very good stuff; it is ADAM WARREN all the way. While I don't think there is anything wrong with Adam Warren drawing whatever the hell he wants to, however the hell he wants to, I don't have to like his work; and really, I don't like it all that much. It's further complicated by the fact that the Dirty Pair (DP) franchise which provided the foundation of his career is, in fact, based on the works of Haruka Takachiho, a Japanese novelist.
There are so many problems with the covers for the Crest and Banner books that I don't even know where to begin. Try reading the links, above; their comments are good enough for me.
I would hope that the covers of the "Crest of the Stars" manga would be a similar situation...but it sounds like it's not.
Still, it is possible to get past lousy artwork--I enjoyed Warren's version of the Dirty Pair comics--as long as the story is halfway decent. CotS and BotS are great stories, and they're great science fiction; the foundation, at least, is solid. But I don't know how they can cram all of CotS into one trade paperback (TPB, which I usually refer to as the Japanese do, tankoban).
CotS is a big, complex story; it favors prose rather than manga--but it could be done, given enough pages. The typical TPB does not contain enough pages.
IMHO, of course.