Sun Tzu's Art of War is a translation of Sun Tzu's military classic by Ralph D. Sawyer (Westview Press, 1994). He has done a fine job and it certainly reads a lot better than the very common Giles translation.
Ralph Sawyer doesn't seem to trust himself though. The historical introduction that he's written is very interesting, but it reads like an examination thesis—too many rambling quotes and not enough narritive for the lay reader.
Rather than throw out the lengthy quotations from other works and put in clear explanations he has relegated the explanations to the footnotes (which are also at the back of the book, rather than on the page with the text). I can't help thinking that it would have been much easier to read if he'd swapped the footnote text and the main text around.
All that said, it is clearly a much better translation than the one you will find on this site. His research is impeccable and the historical explanations are important to fully understand the text and placing it in context.
Read the version I have here, and if you want a deeper understanding then go and get Sawyer's translation too (but you'll need two bookmarks).