Super-sub Neil Harris netted his second goal in two games to level after Noel Hunt's early strike, but a Shane Long effort won it for the Royals.
Jackett, whose team dropped to 11th - eight points off the top six - as a result, said: "I was disappointed with our performance and we can play better than that.
"They were the better side. We struggled to handle their front players.
"We weren't good enough in any department tonight although at different stages of the game I was optimistic. Then Reading moved up and eased away, doing enough to win the game."
On the possibility of bringing players in, he added: "I am always looking to improve the squad, looking to strengthen if we can all the way through until March when the window closes for the season."
Source: PA
Source: PA