Seol Ki-Hyeon's brilliant early strike was enough to condemn West Ham to a fifth successive defeat.
Seol's early goal was enough to give Reading victory
The South Korean fired home from 25 yards with less than two minutes gone, to pile further misery on to Alan Pardew's out-of-form Hammers.
West Ham's Carlos Tevez, Jonathan Spector and Hayden Mullins all had long-range efforts saved.
And Steven Sidwell headed off the line in injury time after Yossi Benayoun's lob looked to be heading into the net.
The Hammers have now failed to score in their past five matches and Benayoun's late effort aside, they rarely seriously threatened the Reading goal.
Manager Pardew had spoken of the need for the team to bounce back quickly from their midweek Uefa Cup exit to Palermo.
But he must have despaired as the Hammers' sluggish start led to them conceding after only 78 seconds.
Seol picked up the ball from Bobby Convey's free-kick and was afforded time and space to pick his spot from distance.
It was a brilliant strike from the Korean but Pardew will be disappointed at how slow his team were to pick up on the danger.
The Hammers proceeded to dominate possession for the remainder of the half but did not look like breaking down Reading.
Carlos Tevez came as close as anyone with a low effort that bounced in a puddle in front of Marcus Hahnemann's goal - but the American held the ball.
Jonathan Spector also unleashed a long-range effort of his own, which Hahnemann gathered at the second attempt.
After the interval, Hayden Mullins saw a drive pushed away by Hahnemann but, in truth, Reading did not look like being opened up.
Two Tevez efforts midway through the second period summed up the Hammers - both flying high, wide and not particularly handsome.
Indeed, Tevez's contribution ended soon afterwards - along with that of Carlton Cole - as Pardew brought on Bobby Zamora and Teddy Sheringham to liven up his attack.
But although the change prompted Reading to increasingly sit back, still Steve Coppell's side looked comfortable.
Only Benayoun, who could barely believe it as Sidwell got back to head his goalbound lob over the bar and out for a corner, came close.
And for all of West Ham's effort, the Royals held on to take the three points that took them up to seventh in the Premiership.
West Ham boss Alan Pardew:
"Given the way that the media react to situations, of course this is going to come down on us.
"We have to be bold and deal with it and we have the character in the dressing room to do that.
"I think the spirit in the squad came through. I think you could say that. We don't have factions in our team."
Reading boss Steve Coppell:
"As soon as we scored we almost had the mentality of holding on. We didn't play as well as I'd have liked.
"They had lots of possession and when we got the ball we gave it away cheaply and that was a concern at half-time.
"The second half was scrappy but the qualities we do have, the way we work defensively meant it went our way."
West Ham: Carroll, Spector, Dailly, Gabbidon, Konchesky, Benayoun, Mullins, Reo-Coker (Harewood 85), Etherington, Cole (Zamora 72), Tevez (Sheringham 71).
Subs Not Used: Green, Mascherano.
Booked: Cole, Carroll, Konchesky, Sheringham.
Reading: Hahnemann, De la Cruz, Sonko, Ingimarsson, Shorey, Ki-Hyeon (Hunt 79), Harper, Sidwell, Convey (Gunnarsson 77), Lita (Long 67), Doyle.
Subs Not Used: Stack, Bikey.
Booked: Ki-Hyeon, Long.
Goals: Ki-Hyeon 2.
Ref: U Rennie (S Yorkshire).