A book rarely mentioned but that had a large impact on me was Carl Sagan's "The Demon-Haunted World: Science as a Candle in the Dark ." It contains his famous dragon in the garage chapter that I still use as reasoning about my not accepting a god as a valid argument. I've probably read over a hundred books on non-belief but that and "The God Delusion" are at the top of my list.

Bertrand Russell, Why I Am Not A Christian

I always recommend my first reading on this subject. Bertrand Russel's Why I Am Not A Christian first printed in 1927. Very enlightening when I read it as a young man.

May I suggest Richard Dawkins ‘s «  The God Delusion »

i found that knowing more about all the traditions, helps you transcend them. you could read about "monotheistic dualism", too.

"God Is Not Great: How Religion Poisons Everything" by Christopher Hitchens. He also probably has 100's of hours of debates, lectures, and conversations on youtube. There are several "best of" video collections of him on youtube (one is something like 7 hours--I found a couple clips in there I have never seen, and I thought I'd seen everything).

I can't remember all the titles I've read, but Daniel Dennett, Dan Barker, Sam Harris, Victor Stenger, and Richard Dawkins have all had interesting books over the last 15-20 years or so. (There is also a "four horsemen" video of Hitchens, Dennett, Harris, and Dawkins on youtube somewhere that I always find endlessly fascinating.)

Richard Dawkins' "The God Delusion": [researchgate.net]

Just about any bible.

Letter to a Christian Nation by Sam Harris

You may like these books by David Fitzgerald:

Nailed: Ten Christian Myths That Show Jesus Never Existed At All

Jesus: Mything in Action, (3 book series)

1. The Bible.
2. The Koran.

The Portable Atheist edited by Christopher Hitchens, it has essays by famous atheists with brief commetary by Hitchens who is very erudite on the subject. He also wrote God is not Great which is a collection of his own musings and thoughts.

Of course reading widely in the fundamental sciences: physics, chemistry, biology will help.

To me a biology by campbell really opened my eyes on the chemical nature of how the cell works. I also took biochemistry, histology, anatomy and physiology classes which goes into the physical science of how living things work.

Yes. The Bible. Reading that bad boy cover to cover is how I became an Atheist in the first place. The book of Mormon and the Bhagavad Gita are equally rediculous.

After that, Virus of the Mind by Richard Dawkins and God is Not Great by Hitchens are fantastic novels.

Good luck man.

I have read several of Bart Ehrmans' books and would recommend any of them :

[bartdehrman.com]

Godless and the Atheist Universe.They have some very interesting arguments and are very well written.

In Defence Of Atheism by Michel Onfray is worth a read

Richard Dawkins and Sam Harris are a couple big names but there's countless others of all stripes. Best bet is to google and youtube. Tons of content out there.

I like Misquoting Jesus by Bart Ehrman.

David Hume, On Religion

I am inclined to suggest reading general science books, catching up on latest science and evolutionary theory, and utilizing a healthy dose of introspection to root out your lingering religious beliefs...or to at least help you continue to question things that you never considered questioning.

Alot of me says that "How to become less religious" isn't something you learn from a book. It's a mindset of continual learning, and actively seeking info and determining the quality of that info. However, Surely there's a book that lays out the anthropology of how humans became humans which might give you a jumpstart. You might start by watching "planet earth" or "one strange rock" with your newfound set of eyes. And, look forward to your new life of learning! Welcome!

I’m hoping to revisit this list and add to my own library.

For the deepest critique of theism, I would recommend “ The essence of Religion” by Ludwig Feuerbach. It offers a philosophically unchallengeable ontology of theism in general and of Christianity in particular.
Karl Marx was very impressed by this book and referred to it in his own writings. His famous statement that religion is the opium of the people derives from Feuerbach ‘s detailed study of how and why man invented Gods .“

I have opinions on a large number of issues but few convictions.

One of them is that man, having invented immortal and omnipotent Gods to defeat/ transcend death, immediately and automagically ( if I may be allowed to invent this term) becomes the creature of his invention. The invented god becomes the creator and man the inventor becomes the created. The greatest feat of magic ever!

To this day many millions of men/women are marked by magical thinking. It is remarkable but really it is no big deal to produce rabbits from hats when it is not impossible to die on Friday and resurrect on Easter Monday.

It is human to despair and to hope. Christianity has magically transformed, or rather , distorted hope into prayer.

Tragically, Christians elevate the practice of praying into the highest form of spirituality unaware that they thus. transform themselves into slavish beggars who live at the whims and/or mercy of Jesus, his dad or his mother known as Mary who is the only woman who so far has managed to remain a virgin even though she has been around for thousands of years.

Well, Feuerbach explains it all.

JC

Below is how the BBC Introduces Feuerbach:

In 1841 Ludwig Feuerbach argued that God was a human invention, a spiritual device to help us deal
our fears and aspirations
This was bad news, because human beings projected all their good qualities onto God and saw him as compassionate, wise, loving and so on, while they saw
themselves as greatly inferior. Thus humanity alienated itself from its true self.

For myself what helped me more than anything was reading books about how the world and the universe as we know it works and our relation to it which enabled me to form a concise and coherent worldview. If you would be interested in going that direction I recommend the following:

Pale Blue Dot, Cosmos by Carl Sagan (clearly shows how minuscule a part of the universe we are); Making of the Fitness DNA and the forensic evidence for evolution (genetic evidence for evolution) by Sean B. Carroll; On the Origin of Species by Charles Darwin (explaining evolution in general); Evolution What the Fossils Say and Why It Matters by Prothero (fossil evidence for evolution); Inside the Human Genome by John C. Avise (shows why it is unlikely the human genome was intelligent designed for us humans).

If you are coming off the heels of Christianity I recommend the following from Bart Ehrman; Jesus: Apocalyptic Prophet of the New Millenium; How Jesus Became God; Forged: Writing In the Name of God; Lost Scriptures, Lost Christianities. These would just greatly help you get a healthy historical view of Christianity.

In terms of learning about physics I recommend Atom by Lawrence Krauss and The Big Picture by Sean Carroll (different Sean Carroll than the first author mentioned)

Welcome, you don’t need any books, being here will teach you lots, or not.

Ishmael, by Daniel Quinn
You will never forget it