The book I put in was Starless Sea, and the five top recommendations I've not read are:
The Last Romantics by Tara Conklin
A Beautifully Foolish Endeavor by Hank Green
Piranesi by Susanna Clarke
The Ten Thousand Doors of January by Alix E. Harrow
The Binding by Bridget Collins
GoodReads have "books similar to the ---" "Goodreads members who liked this book also liked:"
and they give:
The Ten Thousand Doors of January by Alix E. Harrow
The Atlas Six by Olivie Blake
Ninth House by Leigh Bardugo
Babel by R.F.Kuang
Piranesi by Susanna Clarke
recommends
The Ten Thousand Doors of January by Alix E. Harrow
Piranesi by Susanna Clarke
The Midnight Library by Matt Haig
The Song of Achilles by Madeline Miller
Little, Big by John Crowley
BookRiot's quiz: what book should I read next?
recommends
The Tea Dragon Society by K. O'Neill
Then I took the Bookfinity's test, but they are kind of wishy-washy and I don't see anything interesting in their book recommendations. So I decided to add some of my favorite books, and now it doesn't give me any recommendations. :-( So... I don't recommend that.
Ok. I tried again, and now we are getting somewhere:
The Atlas Six by Olivie Blake
The Book Eaters by Sunyi Dean
The Very Secret Society of Irregular Witches by Sangu Mandanna
In the Lives of Puppets by Tj Klune
The Cartographers by Peng Shepherd