From there:
One is The Bhagavad Gita:
>The Bhagavadgītā: with an introductory essay, Sanskrit text, English translation and notes (1948), 388 pages
Another is The Principal Upanishads, also by him:
https://en.m.wikipedia.org/wiki/The_Principal_Upanishads
You could also check out another option for the Bhagavad Gita, by Eknath Easwaran. And other related books by him too:
https://en.m.wikipedia.org/wiki/Eknath_Easwaran
The Upanishads, the Bhagavad Gita and the Brahma Sutras are all about Vedanta, including Advaita (Vedanta). In fact, they are the three main sources about Vedanta, known as the Prasthanatrayi:
https://en.m.wikipedia.org/wiki/Prasthanatrayi
Hope this helps.
I have not read Radhakrishnan's take on the Bhagavad Gita fully. I only read parts of it, when I was a kid. We had many books in that category (Indian spirituality and mythology) lying around at home. So I read some of them.
But I have read one or two other versions of the Bhagavad Gita fully, later on, but don't remember who they were by. There are some pocket editions of the Gita available too. I used to have one. If you are into that subject, I recommend getting a pocket one (along with a bigger one), so that you can read it when you are on the go.
As for Eknath Easwaran's books, I have only read these two: Meditation and The Dhammapada. So I cannot specifically recommend any of his other books. But they are likely to be good, based on his Wikipedia page.
Good luck.
The Flight of the Alone to the Alone, by Osho.
It is about the Kaivalya Upanishad:
https://en.m.wikipedia.org/wiki/Kaivalya_Upanishad
https://www.google.com/search?q=flight+of+the+alone+to+the+a...
https://www.sannyas.wiki/index.php?title=Flight_of_the_Alone...
I have read that book. It is good.
