As your textbook notes, Hellenistic culture grew out of the earlier Hellenic Age. While the former retained many characterisitcs of "classical" Greece, it also went beyond it. Note the exaggerated emotion and drama of the famous "Laocoon and His Sons" sculpture below.
Mystery cults at least partially "filled in" for the loss of civic participation and activism that ended under Philip, Alexander, and the successor kingdoms. Below are images of Serapis, a sort of "combination" god that blended Greek and Egyptian aspects. The new Greek rulers of Egypt wanted a deity that might bring the ruling elite and masses closer together--or at least make the latter more controllable.
Click on the video (above) and try not to freak out over the soundtrack. Just get the broad theme of Zeno's (below) philosophy. The video below--though amateur--is a good explication and explanation of Stoicism.
