This book really assumes nothing. It starts with installing Web Matrix from the included CD and then steps through the basics of HTML using ASP.NET.
The first part of the book is an introduction to ASP.NET, Web Matrix and the basics of writing code e.g. variables, collections and error handling.
Section 2 concentrates on getting and storing data in databases, Microsoft databases that is. But no doubt it can be made to work with other databases. The final section is about your website as a whole. It goes into linking pages and files together, reusable code, cookies and session states. It then goes into Web Services and where to go once you have finished the book.
A very neat book; as long as you are using Web Matrix and Microsoft databases. It does show in many instances the code generated by the Web Matrix tool and the full source for the book can be downloaded.