[sidm83]

I am currently reading the Aitareya Upanishad with commentary by Swami Chinmayananda (founder Chinmaya Mission), but you can find multiple well rated ones online. For Puranas too there are multiple options though I don't think one could go wrong with the translations by Dr Bibek Debroy (leading Economist and Chairman of the Economic Advisory Council to the Prime Minister. Look up his limericks on twitter) who has also translated the Ramayana and only the third person to translate the unabridged version of the Mahabharata.

Otherwise if you can read Hindi and manage to find physical or electronic versions, would recommend Gita Press versions. English ones often come with a multitude of pronunciation symbols (due to the limits of English) which unaccustomed readers may find a bit irritating.