The book is a good starting point for a new as well as intermediate experts having background in developing web applications in ruby.
The book is centered around end to end application development of a sample website and lays emphasis on adding new features over it during the course of different iterations as is done in real life.
Considerable mentions go to deploying the website over Heroku as well as introduction of DataMapper ORM.
While this incremental approach of building a sinatra powered application makes perfect learning for beginners, lack of pointers related to advanced solutions, tackling issues like setting up environment, debugging, etc are felt as the books usability seems constrained by the simplistic pattern it adopts.
After a high level introduction, a basic website is created, using different views. Next, a basic CRUD functionality with database is exposed and the application is deployed live, this is followed by additional DRY concepts available in sinatra and the book caps off its learning with creating modular sinatra applications and enhancing its functionality by demonstrating a custom framework.
Overall, this is a 150 page neat and to the point book for people interested in sinatra.
Note: This book has been provided to me for reviewing under the Oreilly Blogger Review Program.