I was the technical editor for Mark’s book. I quite enjoyed it, it is well written, and accurate.
An interesting thing about the difference between Mark’s book and Jon’s book (for which I was also the technical editor) is that both of them have accurate titles. “C# in Depth” really does go into quite a lot of depth; Jon doesn’t shy away from the abstruse or theoretical, though of course he always has an eye on the practical. Mark’s book really is more about cutting to what is essential to understand in order to get the job done. Both approaches are valid and reasonable.
Bart is a smart guy and I would imagine his book is quite good; not having read it, I cannot offer a personal opinion one way or the other.