Recommended reading - Beginner:
John Shook - The God Debates (2010)
This is an excellent book for high schoolers and philosophy first-timers. Good for dealing with the occasional religious clown.
J.L. Mackie - The Miracle of Theism (1983)
Mackie lists almost all of the common theist arguments here in this extremely thorough tome and goes through the whole gallery of philosophers, from Kant, Kierkegaard, Descartes, etc. all the way up to the likes of WLC or Plantinga.
Recommended reading - Intermediate:
Jordan Howard Sobel - Logic and Theism (2009)
Sobel lays out the complete range of theist arguments, from ontological to cosmological to Pascalian to miracles and the fine tuner. This book is a beast, Sobel is not layman friendly.
Graham Oppy - Arguing about Gods (2009)
Similar to Sobel, covers some more recent philosophers.
Michael Martin - The Impossibility of God (2003)
Martin sets out to prove that not only do the common theist definitions of "God" all contradict each other and even sometimes themselves, but that there is simply no adequate explanation of a theistic God.