The sixth-placed Baggies will be looking to bounce back from their 3-0 reverse at Fulham - their first defeat of the campaign.
"Reading is a good club, well organised from top to bottom," Clarke told the WBA website.
"There is a really good structure and Brian McDermott has been there for a long time and knows the club inside out.
"He's done a fantastic job to get them into the Premier League having suffered a real heartbreak in the play-offs the year before last.
"To get them up the way he did in the manner he did was a great achievement so they will be tough opponents.
"They're a strong team, they're aggressive and they like to put you under pressure."