I love Bierstadt too. There are many excellent books about Bierstadt. You should be able to order specialty art history books at your university library, or even through a larger metropolitan city library through their interlibrary loan service, which is free.
He was one of the premier painters of the American West and is known for his romantic larger-than-life landscapes. You can find his work at many museum's web sites too. Try the Eiteljorg in Indianapolis, the Autry in Los Angeles, the Amon Carter Museum in Fort Worth, and the Gilcrease museum in Oklahoma City. Each of these museums should have information on their web sites. Even the Metropolitan Museum in New York City may have his works.
Best to you.