Two kinds of multidimensional arrays are described: rectangular and jagged. This differs from the C# reference, where only the "rectangular" arrays are considered multidimensional.

I marked this as a serious technical mistake because it can be a source of substantial confusion if you then refer to the .NET documentation. For example, the .NET documentation on Array.Copy describes how it handles multidimensional arrays, and Array.CopyTo is said to work only with single dimensional arrays. Here, however, multidimensional means "multidimensional rectangular array", in your vocabulary, and "single dimensional" includes jagged arrays!

I do see that the book's coverage of Array.Copy and Array.CopyTo carefully refers to a "multidimensional rectangular array" (p. 247). So, at least the book internally consistent. Nonetheless, I still think it would be far better to prevent confusion and follow the terminology that Microsoft uses.