Rista Karljiković was a gymnasium professor between two World wars. He wrote several textbooks on mathematics that were used in Serbian secondary schools at that time, (1922–1941). Four of his books: Trigonometry, Algebra, Analytical geometry and Geometry are digitized and they can be found in the electronic form in the Virtual Library, http://elib.matf.bg.ac.yu:8080/virlib/, of the National Center for Digitization. Retro-digitization of these books is a part of the project on archiving of Serbian mathematical books printed in the past. We explain in this article why Karljiković’s books were selected for digitization and inclusion in the Virtual Library. It appears that Karljiković’s books satisfied very high scholar standards and that they represent very well classroom mathematics taught in the most developed European countries in this period. Also, contents of the books are shortly presented.