Reddit mentions of Buddhism: A Concise Introduction

Buddha was not an atheist. He believed in various gods and assorted heavenly-hellish beings. His main point was that Buddhahood, not godhood, is the highest state that a sentient being can attain. Therefore he lectured heavenly beings and suggested that, because godhood is impermanent, they should study the Dharma with the aim of becoming Buddhas.

On the other hand, "God", as an ultimate good, is not necessarily foreign to Buddhism:


" … Two meanings [of the word “God”] must be distinguished for its place in Buddhism to be understood. One meaning of God is that of a personal being who created the universe by deliberate design and periodically intervenes in its natural causal processes. Defined in this sense, nirvana is not God. The Buddha did not consider it personal because personality requires definition, which nirvana excludes... If absence of a personal Creator-God is atheism, Buddhism is atheistic.


There is a second meaning of God, however, which (to distinguish it from the first) has been called the Godhead. The idea of personality is not part of this concept, which appears in mystical traditions throughout the world. When the Buddha declared, 'There is O monks, an Unborn, neither become nor created nor formed. Were there not, there would be no deliverance from the formed, the made, the compounded,' he seemed to be speaking in this tradition. Impressed by similarities between nirvana and the Godhead, Edward Conze has compiled from Buddhist texts a series of attributes that apply to both. We are told that


“Nirvana is permanent, stable, imperishable, immovable, ageless, deathless, unborn, and unbecome, that it is power, bliss and happiness, the secure refuge, the shelter, and the place of unassailable safety; that it is the real Truth and the supreme Reality; that it is the Good, the supreme goal and the one and only consummation of our life, the eternal, hidden and incomprehensible Peace.”


We may conclude with Conze that nirvana is not God defined as a personal creator, but that it stands sufficiently close to the concept of God as Godhead to warrant the linkage in that sense."


(Buddhism: A Concise Introduction. Huston Smith and Philip Novak. Harper, San Francisco: 2003, pp. 53-54)

https://www.amazon.com/Buddhism-Concise-Introduction-Huston-Smith/dp/0060730676/ref=sr_1_2?keywords=buddhism+a+concise+introduction&qid=1574028674&s=books&sr=1-2

What the Buddha Taught by Walpola Rahula (1974) and Buddhism: A Concise Introduction by Huston Smith and Philip Novak are the classic introductory texts to Buddhism and still used in colleges. In the Buddha's Words: An Anthology of Discourses from the Pali Canon by Bhikkhu Bodhi (2005) is a newer introductory book and more text based.

Secular Buddhist / Buddhist atheist here, for whatever that's worth.

Super-quick and utterly inadequate run-through:

u/Guck_mal is right; the oldest version of Buddhism, Theravada, is pretty damn secular and has very few overtones of anything religious. There are instructions for monks, but Buddha explicitly avoided talk of how the universe got here, the supernatural, etc. Buddha is not seen as a god, but as a guy who figured out how to completely be at peace with the way things as they are instead of how he wished they would be. The ideal of Theravada is (loosely) cultivating individual insight and wisdom. I find myself very drawn to these ideals and consider them much more philosophical than religious.

As Buddhism spread over hundreds of years, a later branch called Mahayana became much more prevalent. This is much more traditionally
religious and features much more iconography, chanting, deities, talk of Buddha as a god, and supernatural features. There's much more talk of karma, reincarnation, etc. than there is in Theravada. The ideal in Mahayana is generally considered becoming a Bodhisattva, or helping others attain enlightenment. While I appreciate the focus on others, I can't get behind the supernatural aspects. Mahayana strikes me as much more religious than philosophical.

I'm a hardcore atheist and reject anything supernatural, but this is no problem within the belief system. Most branches of Buddhism explicitly encourage critical thinking and rejecting what your experience shows not to be true.

Reminds me, I was wearing my "Buddhist Atheist" t-shirt that I got from my sangha (fellow practitioners), and I pulled up to a car wash fundraiser. Turns out it was for an evangelical church group. Let's just say that my attire was a conversation starter.

Some helpful resources:

Smith and Novak's book is a very accessible introduction.

And an obligatory plug for the kickass Against the Stream Buddhist Meditation Society, which I suspect many Redditors would enjoy.