I’m so glad you enjoyed the article, Mick! Although I haven’t read any books devoted to the Gupta Empire specifically, I’m sure they’re out there; and perhaps some of our Indian history experts here in the comments can recommend one. But for overviews of Indian history and philosophy, these are my personal recommendations:
An Advanced History of India can get a little dense (it’s intended as a college textbook) but it provides a very detailed walkthrough of Indian history from the earliest periods all the way up to the twentieth century — with plenty of illustrations, maps and photos.
Sarvepalli Radhakrishnan’s A Sourcebook in Indian Philosophy is one of the all-time core texts on the history of ideas in India. It covers the development of Indian philosophies from the earliest literate periods all the way up to modern Hinduism and Buddhism — and includes plenty of translated excerpts from the ancient philosophical texts themselves.
Thanks for reading, and for taking the time to share your thoughts!