Santi Cazorla bagged the third hat-trick a Spaniard has scored in English Premier League history, while Lukas Podolski and Theo Walcott were also on the scoresheet.
Read on for six lessons learnt during this crucial game.
Arsenal suffer from classic confidence issues.
You look at their poor form (one win from six games prior to the Reading match), then look at the squad of players. Ask the question—how are they eighth?
There's no doubting that the negative vibes surrounding the club have harmed the results, and Monday night just proved that when they're in the mood and on the ball, they can rip teams apart.
It was a classic Gunners victory—67 percent possession and a bucket load of shots, but this time five goals flowed too.
Arsenal have been guilty of playing an incredibly narrow game in recent weeks, with funky formations disrupting the flow and players being used out of position harming the game plan.
Finally, with natural full-backs on the pitch for 90 minutes, the Gunners were able to stay touchline wide, stretch the opposition and open up space between Reading's lines of four.
Kieran Gibbs returned and looked good going forward, providing the cross for Lukas Podolski's strike and outplaying Shaun Cummings with ease.
Not seeing Aaron Ramsey in a ridiculous wide-right position was very, very refreshing.
This was a genuinely shocking performance from Reading, but the back line was the worst part.
Most of Arsenal's goals could have been avoided, in all honesty, with some good communication and a commanding presence in the penalty area, but Kaspar Gorkss was less than convincing on his return.
The one bright spot of Reading's defence this season has been the newly acquired Sean Morrison, but his absence due to injury was sorely felt.
It's been several months in the making, but Santi Cazorla finally played a match where he didn't fade after 60 minutes.
The Spaniard is Arsenal's best player, but his durability in the English Premier League has been called into question on more than one occasion.
It was last-placed Reading, to be fair, and the Gunners dominated proceedings from start to finish, but this was an encouraging showing even aside from the hat-trick he bagged.
With Arsenal 4-0 up, this game was done and dusted.
And still the Gunners allowed Reading a way back into the game—two goals in five minutes from Adam Le Fondre and Jimmy Kebe had Arsene Wenger worried sick.
When will the defence hark back to their early season form when Steve Bould was praised for magnificent coaching and training? When will Arsenal finally maintain the concentration to put opposition to bed and not shoot themselves in the foot?
Following this result, there's a distinct possibility that Reading will occupy last place in the English Premier League on Christmas Day.
The odds are stacked against them staying up, and history suggests they won't, so what should the board do in January?
Common consensus is that Royals fans want Brian McDermott to stay as long as he learns quickly, but 17 games in and he's shown no tactical progress whatsoever.
If Anton Zingarevich continues to stuff his faith into his current manager, how many new players do they need to stay up? This Championship side isn't cutting it.