An anthology including wide variety of xenos shorts, by both known and new writers of BL.

TL;DR: I also written a Codex related table down below so If you want to know which stories might interest you without reading the bunch of paragraphs then check that out.

Warning: It might contain spoilers, and I am a zealot fan so I don't have to approve all works of BL  like many boot-licker bloggers and book reviewers.

1- Gardens of Tycho - Dan Abnett
2- Fear Itself - Juliet E. Mckenna
3- Prometheus Requiem - Nick Kyme
4- Mistress Baeda's Gift  - Braden Campbell
5- Iron Inferno - C.L. Werner
6- Sanctified - Mark Clapham
7- Faces - Matthew Farrer
8- Unity - James Gilmer
9- The Core - Aaron Dembski-Bowden
10- Ambition Knows No Bounds - Andy Hoare

 1- Gardens of Tycho - Dan Abnett
   This story was a total failure, shallow characters, foreseeable storyline, boring...well, of course I'm lying. It is a Dan Abnett story and it is the exact opposite what I said above. Story is about an expert on alien life that is needed by local enforcers to solve a chain of unusual murder cases but as his revelations come to surface the story goes deeper. Definately read it.

 2- Fear Itself - Juliet E. Mckenna
    It wasn't extraordinary but it was readable and it wasn't boring at all. It is about the guardsmen fighting against tyranid hordes and losing. In the heat of battle we see conversations between commisar, medic and guardmens that tells us the horror of tyranids.

3- Prometheus Requiem - Nick Kyme
  This story is about usual Salamander squad of Nick Kyme first appeared in the Salamander series. I dont know if its a prequel or something but it wasn't totally catchy and interesting. It was like the rest of the series; good but not something that you can't stop reading. A default 40K story.

 4- Mistress Baeda's Gift  - Braden Campbell
     A most awesome Dark Eldar story. I don't know how but some races of 40K gets the best stories. Dark Eldar Codex by Phil Kelly had absolutely awesome fluff and this story is like a sideline in that Codex. Braden caught the Dark Eldar logic and lore in a perfect sense and the story itself was both action and lore driven. I even felt sorrow for the characters as the story gone by. So it is good. Read it.

5- Iron Inferno - C.L. Werner
    We usually see Werner write Fantasy  stories and I like his works moreover as this story shows us, he don't lose his talent in case of 40K either. Story begins with a commander planning while an Orc WAAAGH invades his homeplanet. The PDF is ready to fight but they are outnumbered so the commander must be clever and fool the Orcs to win the day. As the action-paced story goes we see Orcs in the heat of battle and It was definetaly fun and I can say Werner caught the Orc logic pretty good.


6- Sanctified - Mark Clapham
    A totally action-driven story about a techpriest working on a damaged Imperial Cruiser. The ship comes under attack by Eldar. And even though the techpriest cannot hope to fight these elite foes he uses his mind to save the ship and the lives of the crew. Totally good story.

7- Faces - Matthew Farrer
    I didn't bother reading this one, but I think it is about Harlequins.  If you are willing to fight through abstract storytelling and lots of descriptions about stuff then give it a shot. Comment me if you want to share your opinion on it.

8- Unity - James Gilmer
    James Swa... no wait. This one is James Gilmer, and I am content that not all people named "James" suck at writing stuff. Gilmer knows what a space marine is, also he knows about kroot and tau. Our story starts on a agri-planet under attack by the forces of Tau. A single space marine and a guardsmen barely survived a recent offensive by the kroot and their objective is to find the means to establish comms with their command structure. Don't say "It is a boring walking story like Ultramarines" because it is not. The dialogues are well written and logical. And when the action kicks in, the story takes a great shape. It also show the horrors of xenos in a good 40K way.

9- The Core - Aaron Dembski-Bowden
    This story is obviously good since ADB wrote it. But If you didn't read the previous Night Lords novels then you might not get it. The First Claw boards a Space Hulk with Raptors on  their side they fought against tyranids to grab important information. As the story goes, action kicks in and Salamander Terminators makes an apperance and STORM BOLTER CHAINSWORD GAAAAAAAAAAAAAAAAAAAAAAAAAAAAH! Got it?

 10- Ambition Knows No Bounds - Andy Hoare
     A rouge trader and her retinue tries to loot an ancient xenos site, then it turns out to be a necron crypt then they get ra...I mean killed. It was fun.

Codex Related Table
Imperial Guard: 2 , 5 , 6 , 8
Tyranid:              2 , 9(We get narration from a tyranid's mind, pretty good)
Space Marine:    3(Related story to other novels - Salamander series), 8(Raven Guard), 9(Salamander)
Dark Eldar:        4
Orc                     5
Eldar                  6(Eldar got his @ss kicked) ,10(Eldar got his @ss kicked)
Tau                     8
Chaos SM          9(Related story to other novels - Night Lord series)

Dan Abnett's story is not related to any codex, It has general "Imperium's inner workings" setting as well as some unique xenos descriptions.              
 
Personal Chart:
Definetaly read: 1,9,4,5,8
Good story: 2,6,10,3(3 - wasn't pretty impressive)
Not my style: 7(Didn't read)