One must read gingerly through The Ontological Argument from St. Anslem to Contemporary Philosophers. The book is not for rank beginners to the subject. There are excerpts the works of philosophers who tackled the Ontological proof for God’s existence, in their own words, with little editorial guidance. Anslem, Decartes, Spinoza, Leibnitz, Kant, and more modern thinkers like G.E. Moore, William P. Alston, J.N. Findlay, Charles Hartshorne, and Norman Malcolm.
The collection is interesting in that is provides detractors comments about the argument; it is strange in that it provides ontological arguments for the existence of God which don’t exactly fit into the scheme as traditionally proscribed (as in Spinoza).
So, if you want to tip toe through the tulips of one of the strongest rational arguments for God’s existence, give this book a shot. But the going will not be easy.