THIS IS A WORK IN PROGRESS
Hi! My name is Draganko from the EU servers. I am not a pro player - I mostly play quick matches. I've been a HotS enthusiast since it was announced. Some time ago, I have gotten a beta key and have been playing since. When I started playing, I bought Kerrigan, and after her - Nova (space girls are awesome). Nova has, since, become my main. I have mostly played the typical Assassinate build and I liked it. This build is something I have come up with when the Kael'Thas patch hit and buffed our level 7 talent - One in the Chamber (increased the auto attack damage buff from 50% to 80%) and made this talent pretty useful.

This build is basically a mix of the typical Holo Build and this talent.

Both the Holo Build and the Assassinate Build were designed by MFPT.
Check him out - he deserves it!

I still think that the Assassinate and Holo builds are viable and I have also put them in this guide (for reference as well), though I will not be covering them here.

In this chapter I would like to explain why I selected the talents I did.
Legend:
This is a recommended talent.
This talent is considered okay, but not generally recommended.
This talent will be probably used rarely.

Level 1

This talent is a great talent on many heroes. Nova is an exception. This talent forces us to lane which is definitely something we should not be doing, therefore this talent isn't that good.

This talent could potentially be useful as the increased range on Snipe might allow it to pick up some kills or it could be used for long range initiating, but as this build is mostly auto-attack focused we don't need the extra range (we would have to come close anyways for an auto-attack).

By far the best choice. Allows for some nasty damage dealing and is used in most Nova builds.

Personally, I like this talent. It can be used for chasing down those nasty ranged assassins or possibly GTFO of those melee damage dealers' ranges. However, the damage on Ambush Snipe isn't worth losing for 4s of a mediocre slow.

Level 4

I see many people taking this talent, even though it's basically useless. You will almost never be able to kill someone with Snipe and the extra 32,5 mana you will get (considering you land the snipe) is useless considering the utility of other talents of the same level.

I find this talent to be the worst of the level. The lower cooldown is bad, at best, compared to Envenom.

This is a great talent for oh-so-many builds. If you do not die you will become a monster. I personally love this talent for the Assassinate and Holo build, but, this only increases Ability Power which is what we are not focusing on in this build.

This is the obvious choice. It has great damage and a mediocre range. Great talent, all around!

Level 7

I also see too many people taking this talent. IMHO, it sucks in every Nova build.

The star of the show!

A great talent, nonetheless. But, we can't take it in this build, since we are taking One in the Chamber.

This talent is mediocre, at best. It probably has some uses, but Anti-Armor Shells and One in the Chamber are much better.

Level 10

Triple Tap is a pretty fun talent which has so many uses. It requires great positioning, though. You must keep in mind that you will be standing in one spot for a very long time and will be a sitting duck, basically. It is also a "selfish" talent compared to Precision Strike as it does not have the same utility as Precision Strike. You should also keep in mind that you will lose Bolt of the Storm to Fast Reload on level 20, so there's that.

My preferred ultimate ability. It has great utility (you can use it when retreating and when chasing people down), global cast range and a fun animation! But, it is much harder to land.

Level 13

This is the talent we will go for on this level. It is pretty useful and allows for some pretty great damage. Couple with One in the Chamber it will make this build crazy good.

This is a great talent as well, though I do not recommend it, because you will be at a DPS loss. The HP regen and the move speed is great in the Assassinate build, but, it will not be as useful here.

This is as great a talent as Advanced Cloaking, if not better, but it isn't what we are going for here.

An awful talent. Sucks on so many heroes, as it does on Nova. You won't be trying to tank damage so you should never take this.

Level 16

It sounds great, but it isn't as great. You won't be trying to AoE so this won't help that much.

Again, a great talent, but not useful in this build. Great for the Assassinate build, but not as good for this one.

Now this is the one we should take. It makes our Holo Decoy not deal 20% of our damage, but 40%!

Again this seems great, but it eats too much of our mana to be able to actually be of help. Nova is mana-hungry as-is. This will only make the problem bigger. By the way, we aren't going for ability damage.

Level 20

As good as it seems! Makes Triple Tap your finisher. It becomes very strong. A must-take if you get Triple Tap.

This isn't THAT good, but it's still pretty useful.

This is crazy on so many levels, I can't even praise it enough. Doubles your damage. 'Nuff said!

Another great talent. Allows for re-positioning or GTFO of a sticky situation. I, personally, take this if I took Precision Strike.

This is a much slower (less burstier) Nova play-style. You should take it easy and weave an auto attack after casting an ability. You should almost always open with Snipe! Your "combo" (if you could call it that) would look like this:
-> -> -> -> ->
or
-> -> (must be done in 1s) -> -> ->

Cursed HollowYou should try to get some easy kills before the tributes spawn. It will help your team, A LOT. When the tributes, themselves, spawn, you should focus on securing kills for your team and zoning, of course.
Haunted MinesThis is probably the worst map for Nova. You should focus on getting kills before the mines open. When the mines open, you should try to kill enemy heroes who are soloing the minion camps, since you, yourself cannot capture them so easily.

ALWAYS put pressure on this hero. He is so squishy that your Snipe + Basic Attack will be enough. He will probably be hiding under towers so use your Holo Decoy. You can find him by looking where his Locust Strain is coming from. Be wary of Toxic Nest.

Not really sure about this hero. The new patch seems to make it like you should avoid him because his beetles might not allow you to re-stealth so easily.

Avoid soloing. Ganking to a half(ish) of his HP is possible, if you dodge the howling tempest and not stay in his Frozen Tempest. He has Block. Keep that in mind.

I do not recommend soloing this hero. Ever. His massive health pool will make sure he stays alive for quite some time. During that period his allies will come and mess you up.

Usually soloable if done relatively quickly enough. Not really much of a threat, except Pixie Dust and Polymorph can be PITA.

I haven't tested soloing him that much. Seems like he is gankable to a point. Avoid Keg Smash.

Dibblez has low damage but high CC. Be careful when trying to gank. Only gankable early-mid game. Has Block.

Honestly, with the new patch, I have no idea what happened to E.T.C.. I think you might be able to gank him. Maybe. His Guitar Solo is pretty bad until he stacks its healing up. Has Block.

Falstad is easily gankable. You probably won't kill him, but you will zone him back, a lot. Be careful of Lightning Rod. Note that he has Barrel Roll.

Such a squishy character. Just kill him. Watch out for rock-it turret though. They will zone you because you won't be able to stealth.

No. Just no. You can't. If he picks The Hunt be VERY map aware of him. He will gank you.

She seems really gankable but her trait Frostbite isn't going to make your task easy. The slow is pretty nasty. Be VERY careful.

I'm having very mixed feelings about him. His Gravity Lapse will knock you up (Pregnant Nova? God, no.). He is squishy. If he has Pyroblast you should try to kill him as fast as possible (when he is casting that is a great time). I recommend to kill him anyways.

Not gankable. A Ravage into a KerriganKombo ( Impaling Blades + Primal Grasp) equals one dead Nova. Has Block but no one in their right mind picks it.

Li Li is enigmatic(ish). You could gank her but be vary of her massive heals, her Fast Feet and her Blinding Wind.

The roots are real. He has low damage (unless he specced for Moonfire, but that's rare). The Entangling Roots are pretty nasty, though. Moonfire's 2s vision can be your demise. Don't overstay your welcome.

This one is a stunner. Avoid soloing him because he could stun you and then slow you, giving enough time for his mates to come.

Nazeebo is easily soloable damage-wise but his Zombie Wall might mess you up. He has a DoT so don't plan on re-stealthing soon.

Soloable but sometimes a pain because of Earthbind Totem and Lightning Shield.

Hunt her always. She is VERY squishy and will burn up like a candle - which is a good thing. Your team wants her dead.