There are few reasons for going from "Reading Books" to "purl.org/net/sopek":
1) The blog is no longer only about books. There are a lot of of posts on various themes
2) I want to promote my global unique identifier "purl.org/net/sopek"
3) I want to promote the idea of global, persistent identifiers
What is this PURL than ?
It is an acronym for Persistent URL. PURL is a service, run by Online Computer Library Center, a non-profit international organization, committed to preserve created PURLs indefinitely and at no cost. There are about 800 thousands PURLs created so far. PURL never change. Once created they will exist as long as Internet will be up and running. On the technical side PURL is a resolution server. It means, that it can point to some real resource (For example purl.org/net/sopek points to this blog). Because of this nature PURLs are ideal as parts of URI for any semantic web need.
And last - but not least - I may decide to move to another blog platform. This means I may loose my sopekmir.blogspot.com address - but I will never loose purl.org/net/sopek !!!