There is a lot more to State of Decay than plain old zombie-killing.
Leave that to games like DayZ, et cetera. There are loads of zombie
shooters. This one is different.

For starters, it's often better to avoid fighting zombies when possible,
than to stand your ground and fight. Killing zeds makes noise, and noise
draws more zeds. Oh yeah, they call 'em "zeds" in this game, despite the
apparently American setting. Welcome to the Queen's English, boys.

Stealth can play a significant role, but this is a sandbox game, after
all. If you want to go around bashing zeds with a pipe threader, by all
means do so. Or you can gun them down with an assortment of firearms,
getting into states of perpetual combat as your gunfire draws more zombies
from all around. Well, perpetual until you run out of bullets. Which can
happen alarmingly fast.

Equally important to the combat is exploration. You survive by scavenging
supplies from the buildings around you - food, drugs, bullets, bats, guns,
fuel, building materials for your home base. Run out of any of those
supplies and you and the rest of the survivors are in serious
trouble. 

One of the more interesting aspects of State of Decay is the ability to
swap between multiple characters. You start off with Marcus Campbell and
his buddy Ed Jones, who doesn't become playable until much later, and
eventually you meet a new stranger named Maya Torres, who joins your group
as a second playable character. Eventually, you come across a small town
with a fortified church at the northwest corner, where you meet a handful
of new characters, some of whom also become playable later on. You meet
others out in the wilderness - by which I mean the town of Spencer's Mill
and its surroundings. Most of the characters are playable eventually,
which is a good thing. Characters tire out after long scavenging hauls and
zombie battles, and need rest, but the game keeps on needing to be played.
Lily is relentless. And sometimes a bit of a nag.

All of these characters have their own set of skills. Marcus starts out
as a fairly decent melee fighter, for example, while Maya and Ed are
weaker in that area. Skills improve over time with repeated use, so all
the new characters you convince to join the group will need to be leveled
up carefully before they are any good at anything. Don't send a raw newbie
out on a Feral hunt, for example, because he'll get literally ripped in
half. Send out someone with a bit more seasoning, and take the newbie along
as backup. Far more likely to survive that way.

An important aspect of gameplay is building and maintaining the home
base. This involves scavenging for supplies, keeping morale up by
completing missions, keeping the group members safe by helping them out of
jams, constructing outbuildings, establishing outposts for resupply and
security, upgrading home-base facilities and other stuff. You may even
need to play out Walking Dead drama moments and deal with troublesome
people in your group. 

For example, you may get a message saying that Maya is storming around
yelling at people, or Ed is scaring everyone with his pessimism, or Alan
Gunderson is being an asshole and threatening to kill everyone. You get
mini-side-missions to go back to base and take these folks for a walk to
"talk some sense into them." In reality, you just take them on a short and
usually straightforward zed-hunt, and watch the dialogue cues on the way
to and from the fight location. Setting the person straight increases your
relationship with that person and improves overall morale.

In the case of Alan Gunderson, you may need to take more extreme
measures. He's the Shane of the game - a ticking time bomb.

Since you are controlling multiple characters, no one character is
absolutely crucial. I found that out the hard way the first time Marcus
got killed, and I got automatically switched to the next character in the
hierarchy. Once a newly-introduced character gets his or her story
commitments out of the way, that character is expendable. Basically, if
you can control the character in any way, the character can die. NPCs will
go out in a blast of glory, detonating their "final solution" grenades
when they are pinned by a swarm of ripping, biting, tearing zeds.
Player-controlled characters will get ripped not-so-cleanly in half. It's
going to happen.

And deaths don't always happen while the player is present, either. Some
deaths happen "off-camera," and you are alerted by a little pop-up in the
top corner. Usually, I manage to find Doc Hanson in time to save Ed from
his injuries. In one scenario, however, I screwed around too much before
getting around to meeting Doc for the first time. Alan shot Ed rather than
let him turn into a zombie, and it happened off-camera while I was out
driving around doing one of Lily's many side-missions.

There's a hell of a lot to do in State of Decay, and a lot of different
ways in which to do it. On the one hand, this makes for very engaging
gameplay, but it can also be kind of overwhelming. Taskmistress Lily is
always radioing in new missions, and you can't possibly do them all. You
end up cherry-picking among them - do you help your fellow group member
out of a jam, or do you scout for the army to target local zombie hordes
for an artillery barrage before they infest a house? Do you go meet Doc
Hanson out at Wilkersons' farm, or do you clear out the two infestations
that are alarmingly close to the church? If you make the wrong choice, it
can have serious consequences to the group. And this wouldn't be so bad,
but it all keeps piling up, and Lily gets on your ass about it.
Occasionally, you might get two or three missions that you really have to
do as soon as possible, and there's no way you can do all three. Your
people will die because of random number generators.

State of Decay is a console port, and it occasionally feels like it.
Character movement can be stiff and awkward at times with a mouse and
keyboard, and controlling vehicles can be a bit challenging. Car-handling
physics are sort of hit-or-miss - some cars seem to have specific
weighting and balance and handling, and others behave more like mounts in
an MMO.

The game is not without technical glitches. For example, Juggernaut
zombies - big, fat monsters that are very tough to kill - are too big to
fit through doorways, but they can occasionally glitch their way into a
house when they use their charging attacks. This can be incredibly
problematic. It happened to me once during the defense of the Wilkersons'
farm when the place was under siege by hordes of zombies. The Big 'Un
smashes into the walls and knocks down all the window barricades around
it, letting the small, regular zombies in. Normally this is more or less
fine, but when the Big 'Un glitches through the wall and ends up inside...
well, that's a position you don't want to find yourself in. Hurl your fire
bombs and eat the loss of trust for setting Job Wilkerson on fire. There's
not really any other way to survive that one.

I found that I rarely used guns for anything. Until you level up a
character's Shooting skill, that character has poor aim, and you need to
score head-shots with nearly every bullet. It's difficult to level up
Shooting, though, because the skill levels slowly, unskilled shooters miss
a lot, and every time you fire a gun, you attract more zombies. Even
rifles equipped with silencers can still draw a lot of unwelcome
attention. Forget about training with a revolver or shotgun. As a result,
most of my characters end up worthless with guns, and have to rely on
fragile melee weapons when the crap hits the fan. And this is the kind of
game where the fan is constantly being pelted by crap. 

There are a couple of ways to build up your guns skill a bit faster. You can
barricade yourself inside a house in the middle of town and score headshots
through the windows as the house gets besieged by all the zombies alerted to
the noise. Or, alternately, most climbable observation towers, like water
towers, road signs or the cell tower in Spencer's Mill, have a platform
halfway up. You can climb up there and snipe from a safe height. You
probably won't get as many kill-shots, but you'll be a lot safer until you
run out of bullets, and you'll have lots more time to aim.

Some of State of Decay's gameplay takes place when you're not even playing
the game at all. This is a bit that I find a little confusing. The game is
"real time," so you can't skip ahead to the next day by resting or skip
through dialogue. You can't wait out the dark and terrible nights by
bouncing ahead a few hours. When you exit the game through the menu and
come back later, no in-game time has passed. But the game has "played
itself" during your absence. Your supply levels will be different, group
morale will be changed, items in storage may have disappeared or been
restocked. Hordes and infestations may have appeared in the town around
you, and powerful freak zombies may have moved in en masse. The longer you
stay away from the game, the more profound these changes will be upon your
return (though apparently they cap out at around 3 days).