
Why I Am Not a Christian is an essay by the British philosopher Bertrand Russell. Originally a talk given 6 March 1927 at Battersea Town Hall, under the auspices of the South London Branch of the National Secular Society, it was published that year as a pamphlet and has been republished several times in English and in translation.
So I'd personally recommend philosophy to people, instead of religion. Bertrand Russell (also known for his mathematical work) is an excellent place to start.
EDIT: For those who disagree, I'd recommend a Russell's essay "Why I Am Not A Christian" [0]. It is quite short and readable.
You could follow up with Why I Am Not a Christian by Bertrand Russell: https://users.drew.edu/~jlenz/whynot.html It's pretty short.
A Devil's Chaplain
Are You Living in a Computer Simulation
Arguing About Gods
Atheism - The Case Against God
Atheist Manifest - In Defense of Atheism
Atheist Universe
Biblical Cosmology
Breaking the Spell - Religion as a Natural Phenomenon
Cognitive and neural foundations of religious belief
Darwin's Dangerous Idea Evolution and the Meanings of Life
Demon Haunted World - Science as a Candle in the Dark
Dossier Of Reason
Evil God Challenge
Forged
God - The Failed Hypothesis
God Is Not Great
Godless
History of God
Jesus Interrupted
Jesus Myth - The Case Against Historical Christ
Letter To A Christian Nation
Logic and Theism
Love Thy Neighbour - Evolution of In-group Morality
Lying
Misquoting Jesus
Superstition In All Ages
The Ascension of Yahweh_ The Origins and Development of Israelite Monotheism
The Christian Delusion
The Dialogues of Plato
The Early History of Heaven
The End of Faith
The Evolution of God
The God Delusion
The God Virus How Religion Infects Our Lives And Culture
The Moral Landscape
Who Wrote the Bible
Why I am not a Christian
These are just some of the books I have read on the subject, but there are others highly rated and recommended that I still want to go through. However, these are really good.
If this list seems daunting I would recommend a shorter list:
"Breaking the spell" by Daniel Dennett "The God Delusion" by Richard Dawkings "God is not great" by Christopher Hitchens "End of Faith" by Sam Harris
But books by Steven Hawking "The Grand Design", "Universe from Nothing" by Lawrence Krauss and "Your Inner Fish - A Journey into the 3.5 billion year history of the human body" by Neil Shubin, are also great although somewhat more technical. All other books are softer read.
Plato. Strangely enough, Plato is probably one of the best introductions to philosophy, not only because he was one of the first whose writings survive to modern time, but also because its relatively simple to read and understand. Some of my personal favorite are 'The Apology', 'The Symposium', and 'The Phaedrus', and of course 'The Republic'. The weird thing with Plato is you'll never know how much of his writings are his thinking as opposed to Socrates teaching. I still reread Plato because the stories (most of his writing is in narrative form) are so damn entertaining.
Aristotle. This is a natural progression from reading Plato. The 'Nichomachean Ethics' is a cornerstone of ancient philosophy and is a relative simple read.
John Locke/Gottfried Leibniz. I'll admit, I struggled through 'An Essay of Human Understanding' but this title and Leibniz's rebuttal 'New Essays on Human Understanding' illustrate a historically important philosophical debate between empiricists and rationalists. Since you're reading 'Common Sense' you might also want to give Locke's 'Second Treatise on Civil Government' a gander.
Immaneul Kant. Since you're reading Schopenhauer you should read Kant as he was heavily influenced by him. You'll hear him referenced a lot if you continue to read philosophy so you should familiarize yourself with his thinking, especially on his thoughts in epistemology.
Bertrand Russell. People have already recommended him and he's one of the most popular philosopher's of modern times, mostly because he's so easy to read and was somewhat of a cultural icon during his time. I have a particular fondness for his work because when I had doubts about my faith, "Why I Am not A Christian" helped me find words to communicate my break with Catholocism. His "History of Western Philosophy" is considered a cornerstone history of philosophy book (although it is somewhat dated now). His writings are usually rather short and concise.
Jacques Derrida/Gilles Deleuze. Now we're getting into some wacky shit. To be fair, I shouldn't even be commenting on it because I have no idea what these guys are talking about half the time. These are the philosophers that people read and pretend to understand because they want to sound smart. You know the stereotypical "philosophy" students that you see in movies. Maybe you'll find something of substance in their work although many philsopher's believe these guys are/were hacks and purposefully obfuscate their writing to hide the fact that there's no substance in it.
One of the best ways to read philosophy is to start with a philosopher who truly changed the game with their work (such as Kant) and work your way out reading the work of his supporters as well as the work of those that disagree with him. This way you'll get a worldy view on 'important' philosophical issues while starting to formulate your own opinions on th ematter.
If you want to read scholarly refutations of arguments for the existence of God, as well as read some arguments put forward explicitly for the non-existence of God, then you have to turn elsewhere: Michael Martin's "Atheism: A Philosophical Justification", Robin Le Podevin's "Arguing for Atheism" and Nick Everett's "The Non-Existence Of God". Another good book from an agnostic rather than atheist perspective is Anthony Kenny's "The God of the Philosophers". A slightly easier read is Julian Baggini's "Atheism: A Very Short Introduction" which is okay. I have some reservations with it, but it covers most of the important arguments and has some stuff about ethics and living the good life and all that happy-clappy stuff too.
As for stuff that isn't concerned with the philosophical arguments? I found Onfray's "In Defence of Atheism" a pretty good read - it is polemical, but is well-written. Nietzsche is always good to read so long as you don't - you know - become a damn goth or whatever after reading it or try and commit genocide or something. Russell's "Why I Am Not A Christian" and the much less read compilation "Russell on Religion" (not widely available outside academia as far as I'm aware) - Russell is a good writer and says some very refreshing things like:
<blockquote>Even if the open windows of science at first make us shiver after the cozy indoor warmth of traditional humanizing myths, in the end the fresh air brings vigor, and the great spaces have a splendor of their own.</blockquote>
