Bookish uses recommendation algorithms like Amazon or Goodreads, but also real editors to make suggestions.
I have only played with it briefly, but I have not been incredibly impressed. You enter a book and it gives you recommendations. More books entered, the better the recommendations supposed to be.
The basic problem with Bookish is that it does not seem to fit a need.
Amazon has the largest database of book purchases and there is no way that any other site will be able to build a comprable database. So Amazon knows what books people buy and how to make recommendations.
Goodreads has created a very useful social media site for readers. Goodreads has user reviews, recommendations, and a very active community. Bookish only has recommendations. If someone has already created a book database (I have over 1000 books and almost 700 reviews and/or rankings), then it is a lot of work to re-create another database on another site. And as far as I can tell, Bookish does not have the ability to import (even though Goodreads can export).
But if you are looking for some new recommendations you might want to give Bookish a spin.