I doubt the Green Trial happens similarly in the books.
I think the only reason it happened in the show was because they wrote themselves into a corner with the High Sparrow and his deal with Margaery and Tommen and what their plan possibly could have been. They needed to get rid of both him and the Tyrells in order to move the Cersei plot along quickly into the next season ready for Dany's invasion because they accelerated her plot to untie the Meereneese knot while Cersei's plot still lagged behind. It would have taken another half-season or so to intelligently resolve the High Sparrow and Margaery scheming so the easiest thing to do was to just blow them up. (I'm glad they did this, it was a cool scene and the High Sparrow dialogue scenes with him sitting on his bench were incredibly boring so I'm glad we got less of that).
Obviously book Tommen is much younger so some of the show stuff won't happen. What I expect to happen is Cersei will succeed in ensuring Margaery is found guilty (much easier for her to accomplish this with Varys getting Kevan out of the way, and book Margaery probably actually is guilty) this will then alienate the Tyrells and they will leave KL, and eventually possibly defect to fAegon. I just re-read the Kevan POV chapter and his inner monologue continually contradicts everything Mace says, harking back to the Robert's Rebellion days. They will side with fAegon if it suits them, and if Margaery is found guilty it will definitely suit them.