I like the style of the Wrox C# series. Their books start from the
basics which could be a waste for an experienced C++ developer through
some of the more commonly used aspects of C# including db access, web
methods, code access security and others. There are some aspects of
C++ that you will find in C# that are not quite the same as you're used
to. The code from Wrox's books is on their website so you can easily
download and compile what your reading to see how it works.
I have 15 books in my office on C# 8 of which are Wrox. I use the
"what book was taken from my office without asking me" approach to
which books are the best and right now I have 8 books left and 7 Wrox
books missing. I don't work for or sell Wrox, I just use them.
As far as tool development do you mean tools for visual studio
integration (like Ghostdoc) or tools that you can sell as add on
components such as component art?