Originally Posted by
Chainsaw_Chimaera
The anime is based of the light novels and short stories by the late Sunao Yoshida (rest in piece). Sadly Yoshida passed away before he completed Trinity Blood, so you won't find an ending in the books either (though the story does go a bit further). I heard rumor that someone would be picking up the work on the novels, but I'm not sure how I feel about that.
The books are split between Rage Against the Moon (R.A.M.) which are a compliation of short stories set in the Trinity Blood universe and Reborn of Mars (R.O.M.) which is the narative of the main story. For example the first volume of R.A.M. contains the story that the Blade Dancer episode of the anime was based on, where R.O.M. covers the three to four part arks of the anime. The books are finally being released state side and you can get R.A.M. and R.O.M. volumes one now.
I really like the stories in the novels and thought the anime was well done. I havn't yet picked up the manga so I'm not sure about it, though I'm told it varies greatly from the original work.