Francis Shaeffer's Trilogy is a complex apologetic if it's precisely an apologetic at all. Rather than a patterned defense of the Christian worldview, it offers a philosophical dissection of those worldviews which compete with it. Shaeffer's three essential books could fairly be one in three parts when overlap is eliminated. Thickly worded, a bit repetitive, though often brilliant, Shaeffer time and again trots out for display the contradictions of materialism, pantheism, liberal theism, etc., the denouement of which is the flipside cogency of orthodox Christianity.
Whether the reader agrees is entirely problematic for everyone finds what they wish to find and no single book is likely to change that. But Shaeffer, on a level visited by relatively few, certainly takes a legitimate swing at it. He offers valuable insight, shows extraordinary range, and unerringly pinpoints the chink in the materialist's armor. Shaeffer's trilogy is by no means a light read, but certainly worth the investment. Should you prefer a primer, try Pearcey's "Total Truth". 4+ stars.