Can anybody suggest me serious tutorial on Snap or book? Can you share your impressions about Snap? I have experience with web programming, but I started learn Haskell and it is great, so I want to wrote site using my new favorite language?
There are definitely no books on Snap. Like all Haskell web frameworks, it's in its early stages.
That said, Snap is a nice clean way to build web applications, and the documentation is very good. Visit http://snapframework.com and click the documentation link. There are tutorials for both Snap itself, and the Heist template engine. There's also a link in the download section to the Snap framework's own web site as a Snap application, which is fairly clean, and a decent way to learn about building simple web applications in Snap.