
I think that
Oriental Mythology is a good companion read to this book.

I think that
A History of Indian Philosophy, Volume 1 is a good companion read to this book.

I have found this online version of value as it contains commentary on individual verses that could assist in the study of the text. Also, there are illustrations that may aid in contemplation.
http://www.buddhanet.net/dhammapada/

I would also like to advocate for the podcast "Waking Up" by Sam Harris as a lot of the content deals with the nature of human consciousness, meditation, and ethics.
https://samharris.org/podcast/

Here is the first chapter of the book, with both the text and audio of the author reading it:
https://samharris.org/podcasts/chapte...

As this book questions the viability of a secular Buddhism I think that this article is a good companion piece:
http://aristocratsofthesoul.com/secul...As the writer of the article states: "My intent in this post is not to demean secular Buddhism in any way, but simply to point out the vast divergences of worldview that comprise this modern movement, and to educate those who might not be familiar with the many differences between modern secular Buddhism and more traditional Buddhist beliefs."

I have read a few books on the following book recommendations by Sam Harris, and all of them have become personal favorites.
https://samharris.org/recommended/?ta...

While I enjoy a wide rang of philosophy, I am particularly drawn to a secular reading of Buddhism. I mainly like the exploration how to achieve a state of personal equanimity, but I also like the ethics and other components of it. Apart from the pure philosophy that has come out of the Buddhist tradition, I also like exploring the mythology in a
Joseph Campbell-like manner. Overall, to make matters short I would say that I generally agree with the approach that is taken in
After Buddhism: Rethinking the Dharma for a Secular Age.
In terms of Buddhist practice, I would say that I am fully committed to incorporating meditation into my daily life. While I have read a number of books on the subject, the book that really convinced me to get serious about meditating was
Altered Traits: Science Reveals How Meditation Changes Your Mind, Brain, and Body.

I recently completed
An Enquiry Concerning Human Understanding by
David Hume together with
Meditations on First Philosophy by
René Descartes. I think that it is a good pairing for those interesting in philosophical skepticism.

I am currently reading
Being and Time by
Martin Heidegger. It is rather dense and requires a close reading, but it has been rewarding so far.

In order to produce a calm state of mind I sometimes make use of a mala (Buddist prayer beads), using the beads to count breaths before I start my meditation session. I have found this method to be helpful at times when I have a bad case of "monkey mind." I would recommend giving it a try to supplement your practice.
https://en.wikipedia.org/wiki/Buddhis...