Ted Nelson's best-known and most influential contribution was not Xanadu, but his book Computer Lib/Dream Machines, which appeared in 1974. Doesn't anyone remember this? It was ubiquitous at the beginning of the personal computer era. This self-published book was very much of its time - it had the same oversize-on-newsprint format and DIY look as the Whole Earth Catalog, which was popular at the same time. It was important because it pursuasively made the case that computing was about to become a medium for self-expresson - a "dream machine" - that was an unheard-of concept at the time. You can use a computer to produce graphics! To play games! How about that! He told about Sutherland's Sketchpad and Englebart's NLS and at a time when these were completely invisible to almost everyone. Xanadu gets a few pages in the book but it is not at all a work of self-promotion - almost the whole book is about the work of others. It's a survey of the computing scene right before personal computers appeared. This book was very timely and I think it provided a lot of inspiration for the personal computer movement. It made you want to try out computing! It has one page about microprocessors: "Here they come ... Microprocessors are what's happening" (the MITS Altair appeared the next year, in 1975).

I think Ted Nelson is one of those people whose main effects are through their influence on others, rather than through what they directly produce themselves.