Town missed out on the chance to jump into the automatic promotion places as Jamie Mackie’s first-half goal gave the visitors the points.
The Nottingham Forest loanee buried a drive into the bottom corner just before the quarter hour after Town had started so brightly.
Daryl Murphy twice went close to salvaging a draw for Blues but the Royals held on to continue their impressive away form.
Mick McCarthy stayed with the same side that beat Fulham last weekend, with new recruits Richard Chaplow and Luke Varney on the bench.
Daryl Murphy, playing in a mask to protect his broken nose, showed all the confidence that comes with being the top scorer in the Championship, exploding through the Reading defence before firing at Adam Federici with his right foot, the ‘keeper equal to the task.
Kevin Bru sent Federici down to his left to gather well with a 35 yarder as Blues pressed for an early advantage, Tyrone Mings’ surging run down the flank stopped by Stephen Kelly.
Murphy crossed for Freddie Sears, who flashed his header wide, then the former West Ham striker tested Federici from 20 yards but against the run of play it was the Royals who broke the deadlock on 14 minutes, Mackie beating Bart Bialkowski with a right foot effort from the edge of the box.
Murphy had a penalty appeal turned down for handball, Hal Robson-Kanu then firing over after Mackie had set him up.
Jay Tabb was close to equalising against his former club, the midfielder getting on the end of Sears’ fierce cross but he couldn’t direct his header in.
Simon Cox had a great chance to extend Reading’s lead after getting on the end of Robson-Kanu’s pass inside the Town box but Bialkowski was out to take the ball of the striker’s toe.
The lively Sears found Teddy Bishop with a flick inside but Alex Pearce cleared the danger, Bishop then showing great awareness to release Mings, the ball again hacked to safety after Luke Chambers had headed back into the box.
Cole Skuse’s brave header saw the ball fall to Bishop in the Royals’ box, the teenager finding space but his shot was straight at Federici as the away side went into the break ahead.
Danny Williams won a free-kick on the edge of the box for Reading after being tripped by Skuse as the second-half got underway, Bialkowski saving well from Nathaniel Chalobah’s strike.
Christophe Berra had to be alert to clear from Cox, while at the other end Bru tested Federici from distance.
Tabb’s cross was then inches away from a Murphy tap in, Chambers’ header at the far post falling into the hands of the Reading ‘keeper.
Bishop’s shot was deflected just wide after Skuse changed the point of attack with a terrific crossfield pass, the midfielder then sending a left foot drive wide from the edge of the box.
Robson-Kanu showed a turn of pace to get away from Skuse, his cross just failing to find Mackie before Blues made a double change just past the hour, Paul Anderson and Jonathan Parr on for Tabb and Bishop.
Bialkowski saved comfortably from Cox, Anderson immediately in the action, taking Murphy’s touch in his stride but Federici kept his goal intact.
Federici was in the right place at his near post to prevent Sears finding the net from Anderson’s cross, Reading making a double change with Garath McCleary and Hope Akpan on for Cox and Robson-Kanu.
Varney replaced Sears for the last 15 minutes and immediately won a free-kick on the edge of the box, Anderson’s strike a yard over.
Mackie wasted a great chance to tie up the points for Reading six minutes from time when he fired wide from close range but the Scotland international’s goal so early on proved the difference, with Murphy twice going close in added on time to rescuing Blues.