William Lane Craig (2010):
On Guard - Defending Your Faith with Reason and Precision
Kindle ebook only 2.65 $
German translation 12.90 €
If you can only buy a single book on rational arguments for belief in God then please do not look further and take this one, as it is the best available introduction for laymen.
William Lane Craig (2008):
Reasonable Faith (3rd edition)
Kindle ebook 21.57 $
This is a must have not only for believers, but for skeptics and atheists as well, because no other book explains the evidence and arguments for theism as good as this one.
Edward Feser (2010)
The Last Superstition - A Refutation of the New Atheism
ebook 15.83 $
Apart from an excellent, even though sometimes polemic, refutation of atheist arguments against theism, Edward Feser presents in this book a simple introduction into the philosophy of Thomas
Aquinas and the concept of classical theism.