To avoid getting too many hits, I use the search phrase "surname AND genealogy" in this initial step to narrow things down, using whatever surname I'm researching at the time.
Next, I look at the listing of digitized books, select one or two that seem most promising, and search within the books for the surname.
- HathiTrust Digital Library allows searching across its catalog and within individual books. Plugging in McClure, I found this page about the Halbert McClure family from Donegal to Botetourt, VA in a genealogy that covered not just McClure but also Haddon and Curry families.
- Archive.org's "Free Books" section has a search box at the top left where I plugged in "McClure AND genealogy" and found 8 possible hits to explore. The most promising hit is A History of Rockbridge County, where Halbert McClure settled.
- Family Search's Family History Books will search across 80,000 books in family history libraries around the country. The search can be general or advanced. Searching simply for "McClure" turned up more than 4,000 entries! I switched to advanced search, added "Halbert" as a second search word, and got only 100 results. Not all of these books can be accessed digitally, however. The one I viewed was McClure Family Records.