We don't know how thoroughly they searched the house, but AFAIK, they have to have a reason to treat it as a crime scene, there has to be some indication there was a crime committed there. IIRC, the house was searched more than once. NO child *advertiser censored* was found. Owning *advertiser censored* is not illegail, unless you are making/distributing it for profit.
IMO, they zeroed in on Shawn from the 1st day and never looked at other possibilities. There just isn't enough evidence to charge him because they still don't know whether she's dead or not. She could have been abducted by some child predator and taken to another state, for all we know.
As far as the true crime literature they found... that's not illegal, either. Many people are fascinated with true crime and the gorier the better. Judging by some of the gruesome theories I've read on these forums, I would say that there are a bunch of folks here who are obsessed with it. JMO, and I could be wrong... if so, it's not going to hurt my feelings.