Plotinus is the only "real" neo-Platonist who deserves the appelation 'philosopher'. The rest are into mysticism and the like.
There are few introduction to philosophy books for undergrads that include the neo-platonists (as I said except for Plotinus).
Neo-Platonism spawned the theosophical movement in the nineteenth century. This was a religio-psychologistic movement that does not resemble philosophy as Plato has laid it out for us.
What you see in neo-platonism is a general deterioration from the heights of reason as attained by esp. Aristotle and Plato. However, historically speaking neo-platonism is important because these 3rd - 4th Century A.D. thinkers help us to fill in some of the missing pieces of the late academy and give us a flavour of how Plato looked to those who were much closer to him in time than we are now.
I'm certainly not a specialist but there is ample resources on neo-platonism around the web.
Neoplatonism [Internet Encyclopedia of Philosophy]
I wish you good luck on your test Arjen!