These books, although they may be loaded with misinformation, are not illegal.
If the government was powerless to do anything about the infamous "Anarchist's Cookbook", which was packed with recipes for bombs and drugs that were (intentionally?) incorrect and likely to injure/kill the reader if actually used, do you really think that the government is could really pull DIY home wiring books off the market?
And we shouldn't wish it any other way. The First Amendment is a wonderful thing...
