Very direct, tons of pressure. His best Dortmund teams were young, played at a ferocious tempo and were extremely aggressive. That being said - those Dortmund teams were also absolutely fucking loaded. It's much easier to play ruthless attacking football when your front line has Lewandowski up top with Marco Reus and Mario Götze playing off of him and Ilkay Gundogan shielding a stonewall pairing of Mats Hummels and Nevan Subotic behind them. The spine of that team was ridiculously strong.
I don't know if Liverpool has the defensive spine yet for the attack to work the way Klopp will want to play. Liverpool have leaked goals like crazy, and Dortmund got away with a lot of things because they had a world class DM in front of a terrific pair of CB's. When Gundogan (who is a horribly underrated player - not only for his defensive work, but his ability to start quick counters with his long passing is superb) suffered a serious injury and effectively missed a season, Hummels and Subotic looked more mortal and Dortmund started shipping goals as well.