What makes Victor H. Mair's Tao Te Ching: The Classic Book of Integrity and the Way by Lao Tzu particularly fascinating is his suggestion that the material collected in the Tao Te Ching (from previous oral traditions) has its roots in Indian yogic texts, specifically the Bagavad-Gita and the Upanishads. Obviously, this is the sort of claim that one would expect from "Llewellyn authors" and other newagers, but Mair is an A-list expert, Professor of Chinese Language and Literature in the Department of Oriental Studies at the University of Pennsylvania, and is considered one of America's foremost translators of ancient Chinese. So, when he writes something (from the Afterword) like:
"There are so many correspondences between Yoga and Taoism -- even in the smallest and oddest details -- throughout the history of their development that we might almost think of them as two variants of a single religious and philosophical system."... one needs to pay a certain degree of attention! His extensive translation notes frequently point out parallel passages from the Indian canon, and in the Appendix devoted to the subject, he traces out a possible timeline for how the ideas embodied in Indian Yoga could have found their way eventually into the Taoist writings (interestingly, he additionally references other scholars' work linking Taoism to Sufism, thereby weaving the major "mystical traditions" into a web worthy of, and perhaps on some levels validating, the Theosophists of the previous century).
This version of the Tao Te Ching is also notable on being based on the "Ma-wang-tui Manuscripts", silk scrolls uncovered in a 1973 Chinese archaeological dig, which pre-date the standard versions of the Tao Te Ching by half a millennia and so provide a much earlier (read: less messed-with) version of the sayings. The differences most obviously manifest in the order of the book, starting with the "Te" (chapter 38 and following in the "traditional" version) and then going into the "Tao", or as Mair suggests, being more a "Te Tao Ching" (which he would translate as the "Integrity Way" book).
Needless to say, I would recommend this book to anybody who has an interest in Taoism, Chinese Literature, or how spiritual traditions interact with each other. Not surprisingly, this is still in print, and Amazon has it at a 35% discount for under ten bucks (and you could snag a "like new" copy for just over a buck through their new/used vendors) ... but it's yet another that could likely be had at from your local bookstore.