As an experienced Java (J2EE) developer and a database consultant, I needed to quickly pick up ADO.NET competency for a client who was going to use both and wanted a database person who understood the two technologies' approach to persistent data (i.e., database access). I also have experience with (pre .NET) Windows development, so I wanted to find concise, clear explanations targeted above the "newbie" level.
This book turned out to be an excellent resource. I blasted across the introductory material on the .NET framework and ADO.NET architecture and dove into the ADO.NET object and method explanations and examples, especially the material relevant to MS SQL Server, which was the DBMS for my project.
The book's organization and many clean code snippets made it very straightforward to have a solid understanding of ADO.NET in short order. More advanced issues will take more time to fully "grok", but I was able to cover the first level well before my client required me to.