I would like to offer a hearty recommendation to a book that came out last year by Shohaku Okumura (the wonderful teacher/priest/scholar/translator/practitioner who has also been the translator and guiding hand for Uchiyama Roshi's wonderful books such as "Opening the Hand of Thought" and so many others). This new book may be the best "say it straight" introduction to Dogen-think (and non-think) out there ...
Realizing Genjokoan: The Key to Dogen's Shobogenzo
I believe that Taigu also has given it a strong "thumbs up" on this Forum a few times, and I have moved it to near the top of our 'Suggested Book List' ...
It certainly continues in much the same style, and with the same clarity, as many of the other Uchiyama-Okumura books such as "Opening the Hand of Thought" and "From The Zen Kitchen To Enlightenment: Refining Your Life (a commentary on Tenzo Kyokun)"
I took my timeless time with it (one reason that I am only getting to this recommendation today!) It certainly is a book to digest in small bits, but written in a way of great ease and clarity in both words and insight. The True Dharma Eye ... yet very gentle on the reader's eyes.
I just found a more detailed review, with which I much concur ...
I give it Five Buddhas (although for some reason the forum only allows me to post 4)!