It appears I am pretty conservative when it comes to programming languages for commercial use. I treated C++ as C with classes until 2005 or so, skipped the STL horrors of the '90s, and have been using Haskell for the last few years ('98 initially but we've been using extensions for the last couple of years... woo!). It is filtering through to me, though, that .NET is probably a fairly mature platform, after 10 or so years!
In contrast, this book was cutting edge. First published in early 2001, it's based on the .NET SDK beta! I bought it in 2003/2004 from a Galloway and Porter warehouse sale, as it was getting out of date at the time (I thought it'd make a good introduction to the basics), and it's been sitting on a shelf of mine since. As most of my work has either high-abstraction requirements (Haskell) or low-level requiremements (C++), C# and .Net has sat in a middleground that I've been ignoring, but it's a gap I should fill in, so fill in I should...
Essentially, the book tells me nothing architecturally that I haven't picked up already, and the details are probably out-of-date, but it's a short (180 lightweight pages) and straightforward introduction that I can probably use as a basic reference (steering me to the right place in online docs) for a while if I start bashing code out, until I get some kind of big new, shiny reference book on the subject. It's pretty much exactly what you'd expect from a slightly rushed beta-technology O'Reilly book!