"Brief Cases" is another anthology of Dresden Files short stories or novellas, akin to "Side Jobs" written by Jim Butcher for a variety of other anthologies or sources. As near as I can tell, Brief Cases & Side Jobs together encompass everything outside of the stand alone main sequence novels, and there are two additional stories in BC that I have never read before, one of which is definitely published for the first time.

The stories are:
Curses - In which Dresden investigates the supposed Billy Goat Curse preventing the Chicago Cubs from winning a world series. Written & published well before the club's actual 2016 Series win.
Even Hand - John Marcone PoV and the introduction of the Fomor
Bigfoot trio - Three stories, alluded to in "Skin Game", in which Harry takes a series of jobs involving Bigfoot, which mostly involve investigating a series of threats to one such creature.
Bombshells & Cold Case - Two stories from Molly's PoV. They bracket "Cold Days", the first is about her adventures with the svartelves, resulting in her apartment, seen in "Cold Days" and the latter is her first mission as the Winter Lady. It has some interesting facts about the position and the mantle which don't exactly jibe with Maeve's behavior, or demonstrate an additional level of psychosis on her part.
Jury Duty - Takes place after "Skin Game" as near as I can tell, where Harry gets jury duty, and the case concerns his area of expertise, so of course he has to do the job of one side in the trial, which AFAIK is illegal as fuck, no matter how much TV writers love using it as an episode plot.
Day One - Waldo Butters PoV, about his first mission as the Knight of Faith.
A Fistful of Warlocks - Luccio's adventures in the Old West when she was a field warden tracking down warlocks. A couple of historical figures appear, both real world & Dresden Files characters.
AAAA Wizardry - This was a new one, to me, at least. Harry is giving a lecture to a group of trainee Wardens about investigating, intercut with a case he worked through the Paranet, which is supposedly his lesson, and the class as the framing device.
Zoo Day - The for-sure original story, about Harry taking his daughter Maggie to the zoo, and of course, encountering paranormal stuff. Split consecutively between three different points of view, giving the same trip through all three perspectives It brings up the interesting concept that there is a whole other world of low-level supernatural menaces that are only perceived by children, and as they mature, are forgotten, so that no adult knows about them.

As with "Side Jobs," almost everything in it is available elsewhere. If all your other Dresden Files books went up in a fire, this is a pretty good thing to have in order to get the stories in one place, and there is the new content, of course. Unlike Side Jobs, the new stuff isn't the first thing since a cliffhanger ending to a main novel. It actually seems like it might be setting something else up, but I'm not sure how I feel about that.