Intro books to the sertting (novella wise, I know you are knowledgeable on the setting) are wolves on the border and heir to the dragon.
I would avoid the stackpole Warrior books. They are interesting in that they are the setting, but they are pulpy in the BAD sense of the term, with caoonish characters and dared writing. Good for their moment, not so good 30 years later. At least for me.
Avoid anything by Blaine Lee Pardoe.
Anything by Szmetzer will be at least acceptable if not outright good. I just read Redemption rift and Redemption Rites back to back. Good duo. the second ones needs you to know about the battle of terra, but as long as you know what the dragoons did there (die as cannon fodder, basically, adter Marotta Kerensky of clan wolf convinced them to be act dumb as a shoe) you are good to go.
Short story books for the BT universe are always good. Not all stories are equally good, of course, but their vignette format plays well with th setting. In this sense the Shrapnel ezines and the BattleCorps anthologies are also an option. They are fairly cheap if you buy back isuees, like 3 or 4 bucks each. In that same line, the Eridani Light horse is probably good, but I have not read it.