Perhaps Oskar is on an "odyssey" to discover the meaning in the things his deceased father left behind. His fascination with finding the correct Black family is one example.
When Oskar goes to Mr. Black's house, he talks about how he made the bed from a tree that was in the park, that links to the Odyssey and when Odysseus makes his bed out of the tree.
Links
Blacks - The last name of the family he is on his "odyssey" to look for.