The Bible.
The first few are written by ex-atheists.
Mere Christianity/ Screwtape Letters
http://family.christianbook.com/mere-christianity-screwtape-letters-volumes-1/c-s-lewis/9780060731878/pd/31871?event=CF
Case for Christ & Case for Faith - Lee Strobel
http://family.christianbook.com/case-christ-faith-2-volumes-1/lee-strobel/9780310608820/pd/608821?event=CF
The New Evidence that requires a Verdict - Josh McDowell
http://family.christianbook.com/new-evidence-demands-verdict/josh-mcdowell/9780785242192/pd/42199?event=CF
The Science of God Alister McGrath (Phd Molecular BioPhysics)
http://www.amazon.com/Science-God-Introduction-Scientific-Theology/dp/0802828159/ref=sr_1_5?ie=UTF8&s=books&qid=1238768939&sr=1-5
The Twilight of Atheism by Alister McGrath
A former atheist who is now one of Christianity’s foremost scholars
http://store.rzim.org/product/tabid/61/p-309-the-twilight-of-atheism.aspx
Prof. Daniel B. Wallace (wrote the textbook on ancient Greek & Greek translation) in an interview in the book "The Case for the Real Jesus" says "It's disturbing that when it comes to the Christian faith, people don't really want, or know how, to investigate the evidence", so I will include some books Daniel Wallace has contributed to.
Reinventing Jesus: How Contemporary Skeptics Miss the Real Jesus and Mislead Popular Culture
http://family.christianbook.com/Christian/Books/product?item_no=42982X&netp_id=446304&event=ESRCN&item_code=WW&view=covers
Dethroning Jesus: Exposing Popular Culture's Quest to Unseat the Biblical Christ
http://family.christianbook.com/Christian/Books/product?item_no=226150&event=CF
The Case for the real Jesus - Lee Strobel
http://family.christianbook.com/Christian/Books/product?item_no=242109&event=CF
You can safely skip these,
The God Delusion by Richard Dawkins
God is Not Great by Christopher Hitchens
The End of Faith and Letter to a Christian Nation by Sam Harris
I paid a $1 for Hitchen's book at a used book store and it was pathetic, I wish I had bought a coffee as for Dawkins and Harris.... I would be embarrassed to be an atheist if these men are supposed to be speaking for me.
They all are like reading a rant by an angry teen that doesn't care about historicity, accuracy, integrity only ranting.
http://www.amazon.com/Dawkins-GOD-Genes-Memes-Meaning/dp/1405125381
In "Dawkins' GOD: Genes, Memes, and the Meaning of Life" Francis Collins, Director of the Human Genome Project say that Alister McGrath
"Wielding evolutionary arguments and carefully chosen metaphors like sharp swords, Richard Dawkins has emerged over three decades as this generation's most aggressive promoter of atheism. In his view, science, and science alone, provides the only rock worth standing on. In this remarkable book, Alister McGrath challenges Dawkins on the very ground he holds most sacred - rational argument - and McGrath disarms the master. It becomes readily apparent that Dawkins has aimed his attack at a naive version of faith that most serious believers would not recognize. After reading this carefully constructed and eloquently written book, Dawkins' choice of atheism emerges as the most irrational of the available choices about God's existence."
The Dawkins Delusion by Alister McGrath with Joanna Collicutt McGrath
" The God Delusion makes me embarrassed to be an atheist, and the McGraths show why."
Michael Ruse, Professor of Philosophy, Florida State University
http://store.rzim.org/product/tabid/61/p-326-the-dawkins-delusion.aspx
End of Reason by Ravi Zacharias
http://store.rzim.org/product/tabid/61/p-63-the-end-of-reason.aspx