Ada 2005 Rationale : The Language, The Standard Libraries

From the reviews:

"Ada programmers will find in this book a well-written and detailed discussion of the changes from Ada 95 to the 2005 version of the language, enabling them to appreciate the innovations, and to regret the omission of features they hoped for. ... For those with Ada experience who are looking for an overview and explanation of Ada 2005, this is required reading." (Andreas Schwald, ACM Computing Reviews, April, 2009)