Below is an issue-by-issue breakdown of no more than three sentences each. At the top of each entry is one quote from a character from that issue which I believe nicely encompasses the most pressing theme of that installment.
Now hold onto your beards, maties, thar be spoilers ahead …!
Book 1: Untitled
"… and shame on the rest of you. Shame on you for giving up." — Hawkeye
Admittedly, I was confused for most of this issue since I had no clue what Hawkeye was doing in the middle of what remains of New York City, much less why it looked like armageddon had come to the Big Apple. And while I finally realized Hawkeye was rescuing a kidnapped and severely beaten and drugged Spider-Man, I can't stand seeing my favorite archer be so brutal with his bow and arrow. The ending splash page with Captain America looking so miserable is a bad, bad omen for what's in store.
Book 2: "Too Many Ultrons"
"This is it? 7,000 superheroes in New York. … This is all that's left of us?" — Spider-Man
It's bad enough to see San Francisco in ruins, but having Moon Knight (out of costume) kill the guy who attempted to hold up Black Widow with a sniper shot to the head is too much. I didn't even realize that was Natasha Romanoff in civvies and donning a hoodie until she pulled her hood off her face. Couldn't Bendis or artist Bryan Hitch provide even a brief explanation for what happened to why her right eye is so jacked up?
Book 3: "The Plan"
"I don't get you at all, Stark. I go out to save Spidey's butt. You all act like I took a dump in the pool. Pym invents the thing that shuts down the world — does all this — and you're like, 'Well, he didn't mean it.'" — Hawkeye
By now I've figured out Hitch's covers nicely provide the gist of the interior story — a lost art these days. Most importantly, this is where the heroes really dig into the moral implications of how the world got into this predicament. The last splash page is a whopper.
Book 4: "Bad Visions"
"We go get Ultron. And we wipe even the idea of him out of existence." — Red Hulk
Book 5: "It All Comes Crashing Down"
"The only good thing that came out of Ultron was the Vision." — Henry Pym
Just as in issue 3, Bendis clearly establishes that this story is talk-y (i.e. dialogue heavy). But it's necessary as Fury has a vague plan to recitfy things using Doctor Doom's time platform, but the heroes now really are wrestling with the consequences of doing so. The moral rubber hits the road as Wolverine makes it clear what he believes is the best course of action: Killing Pym in the past before he can create Ultron.
Book 6: "Head rush"
"Listen to me carefully, bub. … I come from a place not long from now where everything you love, everything, all of it, will be gone … 'cuz a you." Wolverine to Pym
For me, this issue is where AGE OF ULTRON starts rolling. Fury's strike team heads out to destroy Ultron — only to realize Sue Storm (aka Invisible Woman) has followed Wolverine into the past to keep him from murdering Pym. "Past" artist Carlos Pacheco and "present" artists Brandon Peterson — not to mention the colorists — are a creative breath of fresh air, perfect to add some visual fun to this story and depict the stunning Savage Land.
Book 7: "Present … Unaccounted for?!?!"
"It smells like New York. A little different, but the city is still here." — Wolverine
Following the issue I enjoyed the most (followed by No. 9 and the finale), there's this issue that slows down the momentum way too much. On the other hand, we need to see what Pym's murder has done to what's now the present. The highlight of this issue — possibly the entire series — is the interaction and fight between the present Wolverine and his future self when he's a Defender.
Book 8: "Iron Rule"
"You're so like yourself it's scary." — future Tony Stark (aka Iron Man) to the present Wolverine
The Defenders as the future Avengers and an uncaring, Skrull-like Iron Man schticks have gone waaaay past stale at this point. Artistically, there are too many "silent panels;" the Defenders' battle with Morgana LeFey's invading army desparately needs sound effects.
Book 9: "Wolverine versus Wolverine"
Peterson's "present" art is much too bleak for my tastes and again, there are too many "silent panels." "Past" colorist Jose Villarubia makes Pacheco's pencils really pop off the page. The present Wolverine-past Wolverine-past Pym conversation is nothing short of brilliant.
Book 10: "The Epic Conclusion"
"This plan has more ingenuity than you are capable of, Anthony Stark. I feel my father's hand in this." - Ultron
Aside from the "Trial of Henry Pym" storyline in the original AVENGERS title, this single issue gives the beleaguered scientist his greatest time of triumphant redemption. The three-panel denouement featuring Wolverine and Storm hits the right note and tone, given all they've experienced together. The final three pages are a head-scratcher (as in WHT?), but at least it's Thor who fittingly gets the final licking in on Ultron before he gets shut down.