A breakdown of the Upanishads by Parthasarthy. A decent analysis of the texts and explains some concepts well.

When it comes to the more difficult Upanishads, especially those covering non-dualism, Parthasarthy gives an unnecessarily flowery and poetic explanation in a way that wouldn't be helpful for people new to the concepts.

Generally good just because the Upanishads themselves have a lot of wisdom within them.