EarlyWord and CBC Books have recently been the most helpful to me.
Customer: "I am looking for The Revenant. I want to read the book before I watch the movie."
Readers' Advisor: "That might be difficult because there are currently 200 holds on that book."
C: "Really?! Oh, I was looking forward to reading it this weekend."
RA: "The book is widely available to purchase if you are really desperate to read it. I can check availability at the local bookstore for you. Can I make a few suggestions of books that are similar? Do you know anything about the book?"
C: "I heard it was about a bear attack! I like to read books about survival."
RA: "I checked Amazon and the books seems a lot like a Western. Do you like Westerns?"
C: "That part doesn't matter to me so much, I just like to read about how humans survive against animals."
RA: "Okay, I'm going to do a search and make some suggestions."
Your suggestions will likely come more from collection knowledge than search tools. Some subject headings include: "revenge," "trappers" and "wilderness survival." The BookList Reader has this list which can get you started if nothing comes to mind.
The Bear (2014) Claire Cameron
Grizzly Man (2005) film
Into the Wild (1997) Jon Krakauer - book and film
The Tenderness of Wolves (2007) Stef Penney
The Tiger: A True Story of Vengeance and Survival (2010) John Valliant