Way back when Julie’s book was still in her computer, agentless, she wrote a fun post about comps.
She said, “You don’t want to send the agent into hysterical laughter, or worse, tempt him or her to use a trigger finger to delete the query before even reading the rest of it because you came across as arrogant in the comps you chose and how you worded the comparisons. At the same time, you don’t want to use such obscure comps the agent has to look them up on Amazon.”
So yes, it’s a thorny dilemma. The goal is to find titles or authors that might share the same readers, the same shelf in the bookstore. I agree with several commenters on Julie's post; I normally don’t include comp titles in the query unless the agent specifically asks. And it’s always best to use language such as: My story will also appeal to fans of (insert author here) or my story touches on similar themes to those in (insert title here).
The comps I've used when querying for THE LOST LEGACY OF GABRIEL TUCCI are pretty diverse. In some ways my story shares similarities to Alex George’s A Good American with its fish-out-of-water immigrants and ancestral secrets, or novels by Kate Morton and Rebecca Stott with dual timelines and a focus on links to the past. Perhaps even Jennifer Donnelly's novels for themes of betrayal, murder and the seedy side of historic London.
For books with an Italian connection, I actually got a bit of help here. One suggestion came from Julie (thanks for the tip on Pamela Schoenewaldt!), and another, from an agent who passed on an earlier version (i.e. not ready!). “I think the historical Trastevere will find an audience and is very marketable. Have you read anything by Chris Castellani? I think he might be a good comp.”
I loved these books (reviewed them here!) and would be thrilled if mine shared the same shelf. If all goes well, some other writer might use my book as a comp one day.