The invention discloses an adjustable book storage rack, which comprises a shell, a first storage cavity, a second storage cavity and a third storage cavity. The first storage cavity is arranged at the upper ends of the second storage cavity and the third storage cavity, the inner side of the second storage cavity is provided with a first partition plate and a second partition plate, sliding plates are symmetrically arranged on the inner side of the third storage cavity, the sliding plates penetrate through a through groove on the right side of the second storage cavity and is fixedly connected with a baffle plate, a rotary shaft is rotatably mounted between the two sliding plates, and a plurality of placing plates for allowing to be placed thereon are fixedly mounted on the rotary shaft from top to bottom. The plurality of placing plates for allowing to be placed thereon are fixedly mounted on the rotary shaft from top to bottom, and can rotate along with the rotary shaft, thereby facilitating the taking and placing of the books in common use, the sliding plates can be pulled out of the third storage cavity by pulling the baffle plate, thereby realizing the function of capacity expansion, and effectively solving the problems of fixed specifications, fixed sizes and limitations of the existing book storage shelves.