Saturday's FA Cup final defeat to unfancied Wigan proved the final straw for big-spending City, who sacked the Italian on Monday night a year to the day after he led them to the Premier League title.
The post-Mancini era began in haste at the Madejski Stadium, where his former assistant Brian Kidd took caretaker charge for the penultimate match of a frustrating campaign.
Malaga coach Manuel Pellegrini is overwhelming favourite to take over from Mancini, although he would not have learned much from watching tonight's fare.
With Reading already relegated and City's Champions League place assured, the match had a distinct end-of-season feel about it.
Royals goalkeeper Alex McCarthy was one of few outstanding players, making a string of fine saves either side of Sergio Aguero's strike at the end of the first half.
Reading came close to levelling on a number of occasions in a tense second period, only for substitute Edin Dzeko to wrap up a win that secures second place in the closing stages.
However, the match felt like a sideshow to events behind the scenes, with confirmation that first-team coach David Platt would follow Mancini out of the Etihad Stadium coming just before kick-off.
City's travelling support were keen to thank the Italian tonight, with banners held aloft ahead of kick-off and chants in his honour filling the Berkshire air.
On the pitch, City began brightly and James Milner, one of four changes to the side beaten at Wembley, fired over inside two minutes.
Reading started sluggishly and poor defending allowed Aguero a shot at goal moments later, although McCarthy thwarted the Argentinian.
Recently valued by team-mate Jem Karacan at £20million, the Reading goalkeeper did well to block a close-range Milner strike soon after, with Sean Morrison blocking Aguero's follow-up.
It looked as if the ball caught the defender's arm but play continued until Kolo Toure pulled up with what appeared to be a knee injury.
Maicon's introduction resulted in a defensive reshuffle, with only a fine Joe Hart save preventing Hal Robson-Kanu capitalising with a long-range strike in the 19th minute.
Robson-Kanu blazed over his next attempt, before Hart parried a fierce Garath McCleary drive.
Reading were on top and when City did threaten McCarthy was in their way, with a close-range Carlos Tevez header met by a point-blank save.
When it was not McCarthy in their way, it was those in front of him frustrating the reigning champions as Yaya Toure and Aguero both saw goalbound efforts blocked.
City were not to be denied for long, though, as an exquisite short corner routine involving Gareth Barry, David Silva and Milner saw the ball played across for Aguero to slot home with power and precision.
He would have netted an immediate second if it was not for McCarthy's quick reactions stopping the forward's fierce drive.
It was a save matched by counterpart Hart five minutes into the second half as he stopped a point-blank Pavel Pogrebnyak header.
Adrian Mariappa blocked a Tevez strike when play returned to the other end, with McCarthy then turning a fizzing Yaya Toure effort around the post before Tevez blazed over.
However, keen not to go down with a whimper, Reading upped the ante for the final 20 minutes and were unfortunate not to net.
Mariappa saw a header well saved by Hart, with McCleary seeing a fizzing drive deflected behind by Joleon Lescott.
Tevez cleared a Mariappa header off the line from the resulting corner, before Karacan attempted a 22-yard drive that Hart could only save at full stretch.
Yaya Toure and substitute Dzeko both tested McCarthy in that period, with the latter finally extending City's lead with two minutes remaining.
Reading sloppily gave away possession, Silva slipped through Dzeko, who coolly slotted home a second of the night.
It would have been three had McCarthy not stopped Tevez in stoppage time, with the final whistle met by roars of "Mancini".
Source: Manchester City MAD