I went through a full fledged C# book, and it was useless.
In SSIS, 95% of the time you really need basic scripting:
* handling files/directories
* read/ write to a file
* regular expressions
* string/date manipulation
* basic calculations on rows (script component)
* dealing with SQL Server
If might get a bit more difficult if you use the script component as a source/destination, but a C# book won't teach you that.
If you want to design your own SSIS components, that's something else. A good C# foundation can be useful in that case.
But for simple script tasks you don't need boxing/unboxing, object based development, polymorphism, lync, heaps/stacks et cetera.
Regarding the book: I never got around reading it. I just know it exists
It is written by Donald Farmer though, who was on the SSIS team when they launched SSIS 2005, so I have no doubt about it's excellence.
The book is dedicated to SSIS scripting, so you'll learn more about ETL scenarios than in a regular C# book.
Other good books:
* SSIS Design Patterns (not only scripting, but some general good practices about SSIS)
* SSIS Problem Design Solution (one of my favorites. Doesn't talk about SSIS works, but what you can do with it)
How to post forum questions.Need an answer? No, you need a question.What’s the deal with Excel & SSIS?
My blog at SQLKover
MCSE Business Intelligence - Microsoft Data Platform MVP