The first thing to learn is that when you "move up" to version 3.5, you're still "stuck at 2.0". Versions 3.0 and 3.5 of .NET are actually layers that sit on top of .NET 2.0. If you look at the Toolbox in Visual Studio, notice that many of the controls still have a version number of 2.0. This is because only the newer controls and features have been able to the supplemental libraries associated with .NET 3.0 and 3.5. In other words, many of the controls are no different. Furthermore, since the base version is still 2.0, if you're using Visual Studio 2008 (including the Express editions), you can develop in 2.0, 3.0, or 3.5. Thus, any application that you have in VS 2005 can also be maintained in VS 2008.
As for what to learn, given the above books, I would say that these are good books to have. Note that LINQ is a new technology that was not in version 2.0, so if you foresee the use of it in your future development, then definitely focus on it.
Remember that VS 2010 and .NET 4.0 is just around the corner.....