I have read 50 Philosophy Classics, also by Tom Bowdon, which I really enjoyed. I was surprised to find there was an addition to spirituality as well. Given my interest in religion, I thought that would be valuable and put some trust into it based on my previous good experience with the philosophy edition.
I was initially very disappointed that most of the books was modern books about spirituality. Many topics, like science, are things that are hard to go back in history in a way that is still relevant. Spirituality, on the other hand, is in some way eternal, given by self-consciousness and our ability to think about our nature and how to think and act in the world. And given the very long history of religion and spirituality, I was almost offended at the absurdity that most of the books here were from the 20th century onwards.
Even more so because I had a bias against more modern works, but I try to keep an open mind. I enjoyed it a lot more than expected after my initial disappointment. While I still think the modern emphasis is misplaced, there are some benefits. For one, it captures well the modern trend of spirituality. No matter how old the topic of spirituality is, we can't help but live in a culture that is influenced by its modern conception. And thus learning about it is beneficial even if you think it's completely misguided.
Very much like the philosophy edition, I really enjoyed that I could learn about so many different books. It also makes it really easy to see common themes among many kinds of people and culture on how they conceptualize spirituality. For example, the importance of love, giving to others, not being egocentric, and being present in the moment. They all have different formulations and different narratives that symbolize it, but it's a very persistent pattern throughout.
What I love about these types of books is because the content is so diverse that allows me to learn about topics that I would never go into on my own. In this case, what most allured me was books from religions that I know little about. I've read a fair bit on Christianity and Buddhism, but for example, I know close to nothing about Islam. I really enjoyed the writing of Ghazzali and his attempt to popularize Sufism and try to recover the decaying spirituality that he perceived in his region.
My ignorance also extends to Judaism. Here the work of the theologian Abraham Heschel marked the most about the importance of the Sabbath, and how it tries to transform worship from being spatially located (mountains or totems) into being centred around time.
There were several books that I don't think are very high-quality, and of course, those tend to be modern ones. Especially from "gurus" in the East that travelled to the West and gained incredible popularity, which was a virus-like phenomenon in the 20th century. Nevertheless, there were some modern works that were quite solid and deserving of great respect, such as Simone Weil's 'Waiting for God'.
Likewise, even some more ancient spiritual works don't mean that they are that good. While some I consider great classics and incredibly valuable, such as Augustine's Confessions, some were disappointing. For example, Emanuel Swedenborg wrote in the 18th century and very popular. It influenced figures like Blake, Dostoevsky, Helen Keller, John Wesley, and Carl Jung. But while I don't deny that there is some insightful symbolism in his work, as the whole it honestly seemed like the ramblings of a schizophrenic.
It's a great compilation, and while I think it emphasized modern works way too much, I still found it very enjoyable and valuable. The writing is excellent, and each book has a good summary of its themes and some minor information about the author.
I liked that it was so culturally diverse and that the author wasn't afraid to deviate from typical standards. For instance, even Malcolm X is featured. While this may look bizarre, if you read the entry it will make some good sense and I really liked learning about how his spirituality informed his views and what he tried to achieve, especially later in life when he wasn't as radical.
The book also achieves a good balance between not trying to exclusively cater to a more secularized version of spirituality but also having the edition intelligible for non-theists. He wasn't afraid of talking about God in very direct and traditional terms, but likewise, a lot of the works covered can be applied no matter your faith.
It's a very solid edition and highly recommends it if you're interested in spirituality. As mentioned it does have a very modern take on it, but it's a flaw I'm willing to overlook for the overall benefit I got. I ended up with the same feeling as I did with his philosophy edition, I wish the book was twice as long!