Hi Tuxmachina and welcome to this path!
There are two books that were very important when I was struggling with getting acquainted with Buddhism.
The first book I read was the Dhammapada, which is a relatively short collection of saying and teachings directed to popular audiences, and which summerize a lot of the most important ideas of the Dhamma, in a rather poetic way. It is a nice introduction to classical buddhist thought, although it is not recognized as part of the earliest text. It was probably composed (according to some scholars) after the Buddha's demise.
Here you will find a online translation of the Dhammapada:
The second book I could recommend is "In the Buddha's Words", written by Bhikkhu Bodhi, a Theravada monk and expert in the Pāli dialect. This book is a collection of the most important suttas (discourses, sermons and teachings) found in the Pāli Canon (the collection of suttas historically recognized by the Theravada tradition as authentic Buddha's words). The structure of the book is arranged considering some of the key aspects of the Buddha's life and teachings, and it is divided in chapters according to different doctrinal topics, and each chapter with a brief introduction written by Bhikkhu Bodhi himself. It is a long book, but I think it should not be read quickly, but gradually and with time and patience, and it is the best you can find (IMO) if you want to read directly from the source.
In the Buddha's Words: An Anthology of Discourses from the Pali Canon (The Teachings of the Buddha) https://www.amazon.com/dp/B003XF1LIO/ref=cm_sw_r_cp_apa_i_2dbxCb0MRD47T
Here are some useful websites filled with suttas, essays, forums and wonderful introductions to Theravada Buddhism and Early Buddhist Texts:
And since we are in this digital era, I also recommend watching some YouTube channels if possible. Here you will find some of my favorites:
Yuttadhammo Bhikkhu's channel:
Abhayagiri Buddhist Monastery:
Buddhist Society of Western Australia:
Doug's Secular Dharma:
These channel contain sutta clases, dhamma talks, explanations from a secular point of view, guided meditations, etc. I should warn you that some of these wonderful teachers may have different views and interpretations on some doctrinal topics, so keep an open mind and a curious spirit to discern the most appropiate interpretation of the Buddha's teachings. Let experience, attention, analysis and wisdom be your best allies in this path.
And if you find yourself in doubts and confusion, don't hesitate about asking your question here. We all were (and are) still novices on this training and way of life.
Good luck in your path!