This book is simply brilliant, and checking the credentials of the author, a distinguished veteran engineering manager and software architect, one is not suprised in the least. It is one of those special books that pop up now and then - of the kind that would be written by .NET experts such as Juval Lowy or Jeffery Ritcher and a combination of an architectural guru such as Chris Loosley who wrote the now dated but probably best distributed software performance/scalability text ever written High-Performance Client/Server or say Martin Fowler who wrote one of the two quintessential patterns-based software architecture texts, Patterns of Enterprise Application Architecture.
The MS Press Improving .NET Application Performance and Scalability (Patterns & Practices) is similar in spirit and content to Ultra-Fast ASP.NET, but though still useful, it is quite dated (published 2004, that is before .NET 2.0/ASP.NET 2.0) and also much broader in scope and a bigger tome. In contrast, Ultra Fast targets ASP.NET and is very up-to-date, very readable and practical. By limiting the scope to ASP.NET and MS platforms he was able to comfortably and expertly cover all tiers, from the web front-end through the web/app tier to the data and infrastructure layers. Similar books exist for the LAMP platform (e.g, Building Scalable Web Sites: Building, Scaling, and Optimizing the Next Generation of Web Applications and High Performance Web Sites: Essential Knowledge for Front-End Engineers) but this is the only up-to-date such book for ASP.NET and I highly recommend it, as other reviewers have rightly said, for not just the advanced but beginner and intermediate ASP.NET developers, architects and development project managers. I would however, suggest that one gets this book along with what appears to be the quintessential, modern software architecture text - due to its sheer quality and applicability combined with concise coverage of just about all dimensions and viewpoints of contemporary real life software architecture, Software Systems Architecture: Working With Stakeholders Using Viewpoints and Perspectives. Splendid stuff!
I think I may not be alone in believing that a similar text is much needed that would cover the Win-forms/Desktop client application space mirroring the current text. Such a text would delve into the performance scaling considerations of Threading/New Parallel features for multi-processors; WCF/Asmx Web Services, REST/SOAP, ADO.NET/EF/LINQ-PLINQ/other ORMs such as NHibernate, etc. and be structured similarly to Mr. Kiessig's current text. Hope Mr. Kiessig will accept the honor!