Many adults have a fantasy that if they could go back to college — now that the desire to party, drink and sleep around has faded to a burnished memory — they’d get so much more out of it. The publishing industry often reflects this wish. Every season brings offerings that are right at home on anyone’s continuing-ed syllabus: innovative, original ways to study world history through lenses trained on the minutiae of salt or cod, earthworms or spices, tea or telephones. Now, finally, for those of us who wrestled with Rocks for Jocks, pined amid Physics for Poets and schlepped through college on 101s of any and every subject — the beloved survey courses — here’s that most popular professor, Bill Bryson, with a fascinating new book, “At Home: A Short History of Private Life.”