U.S. PIRG Education Fund said 65 percent of U.S. college students reported declining to purchase required books for classes due to the cost and of them, 94 percent said they suffered academically as a result.
The group said the average college student now spends about $1,200 per year on textbooks and other supplies, a figure that's risen 82 percent over the past decade.
Alternatives to buying new books -- rental programs and less expensive used books -- have helped reduce the cost growth but the groups said more and more students are finding it difficult or impossible to afford all the books they need for school.
One option, open-source textbooks, is being encouraged, U.S. PIRG said. The texts are peer-reviewed just like regular textbooks but are available for free to download online and at minimal cost in print because they are published independently by the school or the author.
"In order to have the biggest impact on changing this trend, we need to increase investments in open textbooks and give students access to the high-quality, low-cost alternatives they need and demand," U.S. Sen. Dick Durbin, D-Ill., said.