Gift-Giving at Kids Birthday Parties

For the first time, Oliver attended the birthday party of a classmate, a boy from his preschool class.  Until now, the only birthday parties Oliver has attended have been for the kids of friends.  So I knew what the birthday kids were interested in and what values their parents placed on gifts.  But what do I buy for a child I've never met and who Oliver, at barely three and a half years old, can provide few relevant details about?  Then I remembered that books are safe gifts, at least for preschoolers.  A kid can never have enough of them, they're "educational," but fun, they don't take up a lot of space, so the birthday kids' parents can't hate you for cluttering their house with another plastic object, and let's be honest, they're affordable, so it's a sustainable type of gift for the years of birthday parties my kids will be attending.  So books it's going to be.