…… and I'm curious as to which books I should purchase to allow the greatest flexibility for my players.

I currently own the main rule book, Into The Storm, Battlefleet Kornous, and the GM kit.

If you could give a brief reason why I should pick up a particular title, that would be highly appreciated.

You have a good core of books already. For future purchases I reccomend kronus bestiary, the navis primer, and maybe hostile acquisitions. Kronus bestiary give a ton of xenos stats and info, including all the local major races. Navis primer fleshes out shipboard actions for navigators and astropaths, has rules for ork wierdboys and a stats for all the major races' psykers and thier powers. It also has updated but sometimes hard to understand rules for warp navigation that a debatably better than the core books. Hostile acquisitions gives a bunch more ship components and other options for the aspiring criminal rogue trader.

Cryhavok, thank you for your response to my question. I've been 50/50 on Navis Primer since I saw it in the store. Your recommedation pushes me closer to a purchase. I had not thought about my players wanting to go the more crimminal, or pirate, route. But since I do want to leave them as many options as possible, I'll look through Hostile Acquisitions.

Does the Kronus Bestiary have enough creatures to make it worth the expense? I'm not looking for a D&D Monster Manual. But I would like enough variance on animal to make exporting them a possibility for my players. Also, what 40K game doesn't need a run in with Genestealers? Which brings up the next question. Does any of the RT books have stats for Genestealers, Broodlords, and spacehulks?

Although I think there's a lot of fun stuff in Navis Primer, I do not consider it an essential book unless you want to run an all Ork game, in which case go for it. The expanded Warp Navigation rules are interesting and really well-thought-out, but they turn Navigating the Warp into a mini-adventure run by the Navigator with occasional Charm contributions from other players. It's the sort of thing I'd break out if they're trying a long voyage, but for the most part I wouldn't bother with. There's a lot of good stuff in the Primer, including the new Astropathic and Navigator powers, but it really is a book that focuses on two of the roles on your ship and leaves the rest sort of in the lurch.

Leaving aside the books you have bought (excellent choices), then my next one would be Koronus Bestiary or Hostile Acquisitions. Koronus Bestiary has a lot of fun flavour text entries that can also double as small adventure seeds as they chronicle the adventures of the Galaxy's most patient Seneschal, and then has a Flora/Fauna/Xenos generator in the back so that you have a good framework for creating custom things to try and kill your players. It has some "generic" creatures to run into, and then more specific entries for Eldar, Yu'Vath, Stryix and other Xenos races that you'd run into, plus a few Chaos creatures as well. Hostile Acquisitions has more of a roguish feel to it, and it does have the Nemesis Path as well as alternate ranks and some nice new gear for your players, and it will very much give them more options on how to approach things so it's a really good book for fleshing out the shadier side of Rogue Trading.

I believe that Stars of Inequity has some Tyranid stats in it, as well as a very nice system generator that will help you whip up places for your Explorers to visit, look for treasure and flee from in the span of one session.

Mark of the Xenos for Dethwatch has wonderful stats for Tryanids, Tau and Orks. Plus demons and other goodies. And I highly recommend the Navis Primer as it will help to make your Navagator and Astropath gas more useful and interesting. There are rules for things the Naves and paths can do during shop to ship combat do they are not sitting on their thumbs while the other players are doing all the shooting or flying.

Not to mention the primer had info on the Wierdboy character path that can make an awesom NPC or pc.

Erathia, Digital, thank you for the recommendations. Looks like I will be picking up Navis and the Bestiary, along with Stars of Inequity, over the weekend. I've also taken the time to down load the errata and online starting adventures. So I think I'll have everything needed to start my game.

This youtube review made me buy Navis Primer Hope it helps -

Lady Sonja Blue said:

The Koronous give you the stats you need the most, you will have most stats needed to use the mayor xenos races operating in the expanse as well as a lot of fun beasts and other bonuses. The creatures anathema book for Dark Heresy and the Mark of the Xenos book for Deathwatch can be used to complement them should you wish and the latter is suggested if you want all the Kroot stats you would ever need, both of those other games systems books also include their own rules for genestealers. In the cases of these books you should compare the rules to Rougetrader rules and scale them a bit for better balance. I consider the Koronous Bestiary a must-have unless you have the other systems to steal stats from, the core rulebook has a pitiful amount of stats and the Koronous Bestiary fixes that problem and then some.