Hey all, seen a bunch of posts from people asking about different Necromancer builds/styles and how to play it. After a few run throughs, here's the build I'm currently in the process of doing (only level 22 at the moment, playing on master difficulty and it's worked well so far). Build would be done around level 40 or so.

Destruction
Novice-Apprentice-Adept-Expert-Master
Augmented Frost x2
Deep Freeze
Destruction Dual Casting
Impact

I honestly chose frost for A)RP purposes (I know, I'm a dork) and B)I chose Breton, and with some perks I will be taking in the alteration/restoration trees I should be strong vs casters and frost is highly effective against physical dealing opponents.

Conjuration
Novice-Apprentice-Adept-Expert-Master
Necromancy
Dark Souls
Twin Souls
Summoner x1 *Optional
Conjuration Dual Casting *Optional

Pretty straightforward here. Dual Casting can be very helpful early on, but after you get perm zombies it sort of loses a bit of its luster.

Restoration
Novice-Apprentice-Adept-Expert-Master
Recovery x2
Avoid Death
Regeneration
Necromage (Very important, helps your destruction damage as well)
Ward Absorb

Your 2nd most important tree besides conjurations necromancy line. Don't underestimate ward absorb, NPC spellcasters HURT on master difficulty. You WILL want to use wards, they have received too much hate on these forums IMO. Yes it can drain your mana...but that's why we have perks likes this to help get it back.

Alteration
Novice-Apprentice-Adept-Expert-Master
Mage Armor x3
Atronach
Magic Resistance x3 *Optional

This is the tree that has the most flexibility. If you wear armor, obviously don't take mage armor. Do keep in mind you get 4x the protection when you take this perk. Atronach is incredibly strong, not sure you need any urging to take this one. If you aren't a Breton, I would suggest taking the magic resistance perk unless you have some enchanted on your armor/robes. Still very helpful even if you are because casters really, really hurt at 35+ on master (damn you arch-necromancers).

I'm having a lot of fun playing this way. Just keep in mind this caster is far more defensive than offensive, start fights by getting protection spells up while your zombie and companion (IMO the best one so far is the female dark elf apprentice from the college of winterhold) go in and then start raining frost damage on them. Picking up the regeneration perk in resto fairly early is helpful to keep your companion alive with healing hands, don't underestimate it! If you have any questions, I'm more than happy to answer them

Cool build,thanks for posting this. I am working on building a necromancer/assassin hybrid (Conjuration, One Handed, and Stealth are main skills) but I may take some of your ideas and incorporate them into my build (I am only level 11 or so at the moment).

Great build, sir! I've been wanting to start a new character as a necromancer for quite some time now, but I wasn't really sure where to start. I'm currently still addicted to playing as my Khajiit assassin.