I can also walk into the library and there will be a shelf of free childrens books. Not used, brand new. Stacks of them to take home and keep.
The engine already existed, our public library system.
How good one's library is depends on how well-off the operating local government is. The Imagination Library is more egalitarian because it's often funded at county and state-level, so kids with underfunded libraries get the same level of access as other kids from wealthier zip codes