Great series. My personal favorite from Simmons is the Ilium/Olympos duology, although Olympos was a bit of a letdown at the end. Simmons is brilliant but he does have a way of setting a lot of things up and occasionally failing to deliver a satisfying climax. Hyperion and Endymion, read as two complete works, do a better job of concluding things.
I distinctly remember reading Ilium when I was like 12 and just being absolutely dumbfounded by the erotic scenes with Helen of Troy. I had never encountered adult content like that in a book and it just blew my horny teenage mind.
Simmons’ fusion of historical literature with robust far future science fiction is chef’s kiss.