I've published my extensive review (or, rather, rant) of Nick Carr's «The Shallows» yesterday on my NZZ blog [in German]. Here's a (very short) version of my argument:

Carr argues that the web - or, rather, reading on the web - is tinkering with our brain. Drawing on the idea of neuroplasticity (the fact that our brain is changed by experiences), he cites numerous studies that are supposedly showing that web promotes cursory reading and superficial learning and that, consequently, the human race gradually loses its ability for «deep thinking». 

I have several issues with the book, the first being what I call an overly naive cultural pessimism. Carr for example reminisces about how libraries used to be places of contemplation where books were read, but are now equipped with computers with internet access - ignoring that libraries are (and always have been!) places of access to knowledge - whether this comes in the form of books or not. The scientific foundation of his argument is also shaky: While there is good cause to believe that digital reading is different from "offline" reading, there just isn't nearly enough research to support any of Carr's apocalyptic prophecies.

Most important though, I believe, is the fundamental misunderstanding of how the web works. Carr focuses solely on online texts that have hyperlinks in them and thus promote distraction. He completely ignores all the other effects the web has too, and that (very likely) also have an effect on the human brain - the unprecedented access to information, the ease of collaboration and communication (Clay Shirky even argues that the web leads to a «cognitive surplus»). This makes Carr's book sound like a disgruntled rant from someone who misses the good old times.