Some perspective on the book was in this PF thread
https://www.physicsforums.com/showthread.php?t=121501
which contained this quote from the author referring to his forthcoming book.
In the US now there is a single research group with more than one faculty member working on non-string quantum gravity; at Penn State it has one senior and two junior faculty. Apart from Penn State, and a single person who left Penn State and got a position largely on the basis of his work in another field, the last time there was a new faculty position in the US for someone working on a non-string approach to quantum gravity was 1990. There are at most 4-5 NSF funded postdocs now in the US that a non-string quantum gravity person might apply for...
The situation would be vastly improved if there were open competition on the basis of quality, originality and promise for the large number of postdoc and faculty positions controlled by string theorists...
As far as someone wanting to do a Ph.D. in non-string quantum gravity, there are many and indeed the number of applicants is increasing dramatically because of the visibility of recent important results. But there are very few places in the few groups around the world where this work is done. We literally turn away good applicants weekly who apply to our group. As a result, an increasing number of very promising students are doing PhDs in non-string quantum gravity on their own without the benefit of an advisor in the field.
The only advantage of this is that the few young people who persevere against these odds have visibly much more creativity, intellectual independence and courage than their counterparts in trendy, mainstream fields. So they do better science, and indeed young people are responsible for the bulk of the new results and ideas which have driven the fast rate of progress of recent years. So it is getting increasingly evident that their exclusion from consideration for the best positions cannot be justified on any objective scientific basis.
And yes, my forthcoming book is not an attack on string theory, it is an examination of how this kind of situation can develop, which hurts not just many of the best young researchers but the progress of science itself.[/size][/color]
Smolin was clearly angry (I would say) when writing this. But I would not say that he was mad at string theory (the mathematical theory itself). He has done a fair amount of string research and written (I forget how many) string theory papers. I expect he has a good feel for the rich interesting possibilities of that formalism. I suspect what he opposes, both in this quote from Woit's blog comment and in the book, is the research MONOCULTURE that has developed in fundamental physics.
I could be wrong, plus the book is not out yet and all I've seen is some recent essays by Smolin on the same theme.
E.g. the June 2005 Physics Today piece "Why No 'New Einstein'?"
the January 2006 piece in the New York Academy of Sciences Update "A Crisis in Fundamental Physics"
Links to these are here:
https://www.physicsforums.com/showthread.php?p=1001041#post1001041
In any case that is my take---string may be a rich interesting formalism (although pursued without accountability to experiment) but he quarrels with what he sees as monopolistic mismanagement of theory resources.