serendipity \se-rehn-dip-i-tee\ (noun) - The act of making a fortunate discovery by capricious or quixotic accidence or such accidence (fortuity) itself.
"Rick had not breathed a word about his plans to learn C++ and yet Marge brought home a book on the subject because she was interested in it as well, making for a serendipitous experience."
This word was coined by Horace Walpole, an 18th-century British author, from a fairy tale called "The Princes of Serendip" ("Serendip" was the former name of Sri Lanka). In the story, the eponymous heroes wander around, making unlooked-for discoveries. "Serendipitous" is the adjective; "serendipitously," the adverb. A person given to serendipitous discovery is a "serendipitist." "Serendipity" is a word that is a bit ironic and often slightly misused: for a discovery to be serendipitous, one must not be looking for it in any way.