Whatever you want to read, don't limit yourself.

There are no such books. We each have our own path. There is no one ideological dogma.

Any book their heart desires ....

Not just atheists but everybody who is serious about acquiring knowledge would do well to read literature which challenges their world view. If you only immerse yourself in texts or ideologies which re-enforce your belief system, their is no advancement in your outlook and consequently your ideology becomes a self-referencing loop. As I am sure you are aware this is frowned upon in most academic circles. The most dangerous claim from any individual/group is that they know the Answer or the have the Truth. This is especially true of Manchester United supporters who think they are the greatest soccer team ever!

The Demon Haunted World by Carl Sagan

Read whatever your curiosity leads you to. It's not a matter of what you read so much as whether you THINK.

That said, The God Delusion by Dawkins and God Is Not Great by Hitchens are good sources to fire up those critical processes.

Hitch Hikers Guide to the Galaxy. Says it all.

The New Atheist Trilogy, consisting of The End of Faith by Sam Harris, The God Delusion by Richard Dawkins, and God is not Great by Christopher Hitchens.

Read as much as you can with no limit on topics. Knowledge will set you free.

"The Age Of Reason" by Thomas Paine. In plain speak, using simple logic, it refutes any authority claimed to be had, in the Biblical scriptures. I highly recommend it.

I'm 3/4 through God is Not Great by Hitchens. Highly recommended.

depends on your intent. I would read views contrary to yours so you can flex your brain

Read everything.

Try to read some good historical groundings. A little by the Greeks, a little by the Stoics. Spinoza. David Hume. Then read some good modern perspectives. Joseph Campbell. Then dive into the modern atheists.

Anything - Its funny you reminded me of an encounter in Spain - When Franco died many of us went to Spain to celebrate - my partner and i with two children went to a campsite and politely asked where we should pitch our tent. The owner made this amazing smile and laughed & threw his arms in the air and shouted 'Anarchista!' Anywhere! at all!

Whatever books they want to read, so long as it's with a logical and critical, thinking mind.

Read religious texts it's easy reading /watching something you agree with. It's harder challange your ideas.

The Hitchhiker' Guide to the Galaxy (entire series) : Douglas Adams
Dirk Gently's Holistic Detective Agency : Douglas Adams

Bloom County: The Complete Library Book Series : Berkeley Breathed

On Nation Under God: How Corporate America Invented Christian America : Kevin Kruse

Pilgrim Withdraws: The Rebuttal to Pilgrim's Progress : Benjamin David

The Storytelling Animal: How Stories Make us Human : Jonathan Gottschall

The Bible, you bunch of immoral heathens!!!!!!

If I'm understanding the context of your question correctly, I thought Michael Shermer's 'The Believing Brain' was a pretty decent read.

He goes into lots of different beliefs, including conspiracy theories, ghosts, etc. Kind of complex, but I liked it.

Why I Am Not A Christian, Bertrand Russell

I don't know about any of you guys, but if you read the bible and know how to decipher it. It says these events are none existant. Really

If you are looking for both intellectual stimulation and increasing your knowledge go to the In Our Time podcasts from BBC Radio 4. Melvyn Bragg and three guests (experts in their field) discuss a different topic each week. The show lasts for 45 minutes. Each topic under broadly speaking five categories, Philosophy, Culture, Science, Religion and History. Recent topics have been Henrik Ibsen, The Proton and Beethoven. Erudition at its finest delivered with humour and humility. On top of that each episode from the last 20 years is available as a podcast, over 500 in all. Just go to the In Our Time website [bbc.co.uk]
and you will never want for intellectual stimulus again!

Try Small Gods by Terry Pratchett.

And Sock by Penn Gillette.

And for nonfiction everyone should read Ain't Nobody's Business If You Do (the Absurdity of Consensual Crime in a Free Society) by Peter McWilliams. That last looks like a major spider killer and far more intimidating than it is. It could so easily have been dry and depressing but it's neither. Extremely readable and a most approachable take on blue laws and such.

What suits your fancy

The dictionary