Ambivalent, ambiguous and contradictory the Upanishads are - but only ambiguous because they say one thing and then another; up for grabs, open for diverse and conflicting interpretations so far as coherence goes, if you have a bag for coherence.
I'd previously read the Radhakrishnan and Hume versions of the major texts. Both authors have difficulty bringing the texts around, because they try to; I guess those Victorian gentlemen couldn't help but have some sort of predilection toward coherence and liked to persuade a little consistency, in favour with their own preferences. Olivelle doesn't bother with this. He claims he has avoided personal and interpretive input, suggesting his job is merely to give us the raw texts, as they might have been at the time of writing, ignoring the mass of interpretation and smoothing readings that have intervened, sticking to an orthodox, archaeological understanding of what the understandings might have been at the time - as if that itself were no interpretation. I've never believed this self-effacement in translation - or anything, once some thing is preferred to another! ;] - this transcendence of conditioning which yet remains in the relative world. However, apart from this fatal disavowal of the workings of karma in his own production; it is quite refreshing when someone at least tries! He does let the bricks of the edifice stand by themselves, however higgledy-piggledy, without trying to hone them or trowel some mortar in. So, I reckon, this is probably as literal a transcription as you're going to get.
One minute the texts laud duality, the next they return to non-duality. One moment monism, the next god-knows-what. One moment a transatlantic manifestation of non-difference, the next; division into heaven and earth. So, make of them what you will, it is your self you're reading.
A nice affordable scholarly translation. The only problem is the book feels squashed. You have the spirit of India crammed inside a book the size of a novel, with small print and grey paper. So this Oxford printing isn't a joy to hold in your hands and the notes are a tiny 8 font print!
The upanishad are meant to be printed in a big hardback with a nice big font. What's wrong with Oxford?