BjarneStroustrup on the various forms of the third edition: The "special edition" is the hardcover version of the 3rd edition. It differs from the early printings of the 3rd edition by about 1,000 corrections and clarifications, by two new appendices (just over 100 pages; also available online, see below), and by an improved index. The only difference between the current printings of the special edition and the 3rd edition is the cover (and the price difference implied by that stronger cover). (http://www.research.att.com/~bs/3rd.html)
See also CeePlusPlus