Yes, it's drastically different. Besides the fact that Visual Studio 2003 had a lot of issues in, among many other areas, the designer, the underlying .NET and ASP.NET frameworks have changed a lot.
New ways of working with data (new data source controls, LINQ), new ways to handle security (new Login controls), many language enhancements (generics, anonymous types) and many more features have been added since the release of 1.1.
I would suggest you get a book on ASP.NET 3,5 (like mine
) as a book on 1.1 is really outdated....