There might be some truth to what he says. Eckert Tolle has also written the book The Power of Now, whichs concept basically is that you should let negative thoughts pass through your mind instead of focusing on them. You can do this by meditating for instance. If you read the book it will make sence
I do not think though that the book in itself is a cure. A very troublesome thought might not be able to simply pass through you consciousness - for instance I am always going to be an outsider - unless you have dealt with that thought through analysing it.
A better book i think is overcoming social anxiety and shyness from Gillian Butler. It is a cognitive behavioral approach to getting over social anxiety.
Cheers