This is a decent overview and analysis of the philosophy of Plotinus, coming in 2 volumes with around 500 pages in total, originally given as talks in the rarely uninteresting Gifford series of lectures. The author was a former professor at Cambridge, and Dean of St Pauls, and much of the book discusses how Neoplatonism and the philosophy of Plotinus share their substance with Christianity, due in part to the large influence that it had during the early years of theological scholarship.
The chapters focus on different aspects of Plotinus' writings: matter, soul, spirit, religion, aesthetics, morals, and The Absolute. The absolute is an interesting, if currently unfashionable, philosophical concept. In Plotinus it comprises Truth, Beauty, and Goodness - concepts drawn closely from Plato. The idea is that these three things possess absolute reality, not being relative or constructed concepts as some philosophy has them, nor contingent as the material world. Truth, of course, does have absolute existence, provided we only mean necessary truth (such as mathematical truths), and not contingent truth, but I find it hard to be without some doubts that the other two have absolute reality, though the Greek meaning of these words is not identical to typical English useage. Goodness and beauty more commonly feel like they are relative, in reality, but Plotinus answers this with the claim that our experiences of them are generally imperfect copies of the original and perfect forms of them that exist in a comparable way to Plato's forms. Together the three things form the One, which shares a lot of properties with God, being outside of space and time, Eternal, the highest stage of reality, and having perfection.
Much of what is attractive and convincing in Plato is to be found in Plotinus, though in a much different format. There is not the irony and other rhetorical devices of Plato, though this of course makes the reading less entertaining, though less easy to misunderstand.
What may seem an irony though is that Plotinus was a pagan, and didn't like Christians, but his philosophy is probably the only system that pretends any sort of completeness while also being largely compatible with Christian theology. As the author writes:".. we cannot preserve Platonism without Christianity, nor Christianity without Platonism, nor civilisation without both."
I would recommend this book to readers interested in philosophy or religion. More will be gained from reading it if a reasonable familiarity with Plato is already had, as many of the important concepts discussed here are originally from Plato, and will not be straightforward or convincing if they have not been covered separately and in more depth. ( )