This is an excellent treatment of the MSIL topic at just the right level if you're in need of nitty gritty details for debugging, disassembling, or generating IL code. Coverage of the PE format for managed executables is the best I've seen. The text is well-written, the examples are clear and concise, and the diagrams are very helpful. The book can be used as both a tutorial and a reference: the appendices include an ILAsm grammar reference, a metadata tables reference, and an IL instruction set reference. The book is also available electronically to owners of the physical book.