The Marin County Free Library this month discarded 7,500 items of mostly adult and teen fiction in the midst of growing dead stock that library managers attribute to the rising popularity of e-books and tablets. 

The sweep removed about 3.5 percent of West Marin’s stock, or about 1,900 books—though in the weeks since the “weeding,” additions expanded the stock in the area’s four branches above previous levels. It was the largest removal of dead stock since 2010, according to sources in the library system. 

That year, when 18,000 books were removed, the library adopted an official development policy that placed the highest priority on retaining materials actively checked out by patrons. 

Books that aren’t checked out or used in-house for two or more years are tagged for removal, though exceptions can be made for books of local importance.

“New things do really matter, and it’s important to keep it fresh,” Sara Jones, the library’s director, said.

The branches have limited shelf space and strive to display books in an inviting manner rather than stuffing shelves, Ms. Jones said. They also must accommodate the continuing influx of new books, especially bestsellers. The system has 62 copies of Sue Monk Kidd’s “The Invention of Wings,” currently second on The New York Times Bestseller List, and 79 copies of John Grisham’s “Sycamore Row,” number three.

Donna Mettier, the technical services manager for the library, said about 35,000 items left the library each year through de-selection, deterioration, loss and theft, while 70,000 items are added annually. 

While removing books can elicit visceral reactions, and in the past concerns have been aired about impacts to the diversity of library stock, Marin patrons can order books through Link Plus, a consortium of California and Nevada libraries, Ms. Mettier said. 

Nancy Hemingway, the head librarian in Inverness, said her shelves get particularly crammed because villagers often check out books over the hill but return them to their home library. 

Discarded books are offered to local organizations and nonprofits first; West Marin School is receiving roughly three boxes, with 30 items each, Ms. Hemingway said. The rest will be sold to a company, Better World Books, which sells books to fund literacy programs or donates books outright.

As a last resort, Ms. Jones said the library would recycle any remaining unwanted books, “so that nothing is in a landfill.”