In the book: Trip is the second-oldest Richardson kid, and he fits right into the "handsome, obnoxious jock" trope. He develops a relationship with Pearl after they nonchalantly go from studying together to having sex. Over time, it becomes clear that Trip actually has feelings and isn't a total jerk — you know, the typical storyline for the dude-bro with a bit of depth.
On the show: Trip is still the "handsome, obnoxious jock," but we see a few moments in which he tries to break out of the superficiality mold. Being with Pearl helps him do that, but something about their romance feels a little off. It might be the way it develops. During an intimate study session, the two start making out and decide to have sex (similar to the book), but before things progress too far, Trip jumps out of bed and snaps on Pearl for enticing him when it's obvious that Moody likes her (unlike what happens in the book). He later claims that he just feels like Pearl is too good for him, but it's not sufficient enough to excuse his earlier outburst. Sure, Pearl forgives him and they continue seeing each other, but his character development is less convincing.