Currently, the only (searchable) site on the net where I can get an opinion on a book is Amazon. Amazon also has the listmania and “customers buying this book bought these as well” guides. These help to evaluate the network of related books. I remember coming across another site where upon entering one’s preferences, one got a list of recommended books, but whose name I can’t recollect now.
Are there any such sites anymore? Ones that guide you on related books, based on a certain starting point and/or where users aggregate reviews on various books they’ve read recently. Preferably non-fiction.
I’m not sure what you mean by “searchable.” Dropping the title and author into Google usually turns up a number of reviews on most books. (Admittedly, about 80% of them tend to be copied from a single source.) I haven’t looked in a while, but I thought Barnes & Noble had a review section similar to Amazon’s.
I was surprised to find that The New York Review of Books does not have a search feature, but I also found that with the Google Toolbar installed, the “Search this site” options works quite effectively on the NYRB.