I whole heartedly disagree... whil Nielsen's book should be on your list to read, it most definitely should not be first.
Read a real design book by a (semi-)contemporary print designer first. Learn composition. (David Carson, Kyle Cooper, Neville Brody, etc)
Then... Read Edward Tufte's three excellent books on visual displays of quantitative information such a charts, graphs and interface. You will gain insight as to how to place a substantial bit of information into a usable package.
Afterwards pick up a book on motion and and animation (Hillman Curtis, Joshua Davis, film books are also good) As the web most certainly needs motion to remove monotony and also give motor clues as to how your site(s) work.
Then, maybe you could look back on Nielsen again and give him a good read. Take it in. But do not fall prey to his beliefs in purely functional non-design.
You will be lost then. Good luck.