The Book of Honor is The City and the City by China Miéville.
The City and the City was published in May 2009. Awards include the Hugo Award, Arthur C. Clarke Award, World Fantasy Award, British Science Fiction Award, and the Locus Poll Award. It was nominated for a Nebula and the John W. Campbell Memorial Award.
Michael Moorcock reviews The City and the City in The Guardian: The spaces in between
Abigail Nussbaum reviews The City & The City
On BLDG BLOG: UNSOLVING THE CITY: AN INTERVIEW WITH CHINA MIÉVILLE
Potlatch members nominated twelve books for the Book of Honor. You can see the nominees and the discussion at the archived Book of Honor Nomination page.