It's the proper order in which to read these books, I think. Not only because the latter came 52 years after the first of the trilogy volumes, but also because it's interesting to see what she did with the raw material before actually getting to know the raw material.
I say this because I started reading them in the opposite order and wasn't happy about it. So I saved the memoir for last — and am glad I did. Here's a passage from it about Drewsboro, where O'Brien grew up:
On either side of the track there were grassy banks full of wildflowers and burdock and flowering weed, bees buzzing and disporting themselves in and out of these honeyed enclaves, and the smell of the nettles so hot. Birds swooped in random gusts, and butterflies, velvet-brown, maroon, and tortoiseshell, their ravishing colors never clashing, never gaudy, moved in the higher strata, like pieces of flying silk.
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