I am not convinced that Amazon extending the searched material in 'Books' to include the 'excerpts' is a good idea. I was looking for a copy of T.S.Eliot's Social Criticism by Roger Kojecky which is in Amazon's catalogue but searching was not very successful. As it is a older academic book it has of course been quoted quite a lot in subsequent books on T. S. Eliot or on modernism. So instead of offering me copies of the book I am looking for, I am confronted with a list of books that quote Roger Kojecky's volume. Just look what you get searching for T.S.Eliot's Social Criticism by Roger Kojecky . Poor old Kojecky doesn't appear until items 9 and 10. Now the first time this happened you might scroll or even look on the second page of listings but if you're searching for a lot of items having to burrow through recent books that quote the one you're looking for is a serious pain.
Having said that, I am very taken with the one that appears first on the list Print for Victory: Book Publishing in Britain 1939-1945 by Valerie Holman so maybe as a sales technique it has some points!
Edited to add: that searching for The Poetry of T. S. Eliot by Maxwell is even worse as the excerpts triggering appearances in the search result are only there because they contain the words 'Eliot' and 'poetry'. Seriously, just look! That's really going to narrow the field! Back to my frustrating searching.