Problem-solving ability is one of the essential skills needed in the 21st century. Therefore, there has to be learning media that supports students' problem-solving abilities in physics lessons. One teaching material that is very suitable for the digital era is a digital book, commonly called an ebook. This study aims to determine the effectiveness of digital books in improving problem-solving over the past five years, 2018-2022 taken. This study uses a literature study method that includes reputable international and national journals. From the study results, it was found that during the last five years of the 30 journals we have reviewed, 98% that use of digital books was effective in improving problem-solving skills. This digital book can also improve some of the skills needed in the 21st century. Digital books have many advantages, including lots of pictures, graphs, phenomena, and animations that are relevant to learning physics, making learning physics more fun, and developing students' creativity in exploring and learning physics. Besides that, the drawback of digital books is that they can tire your eyes because you have to linger in front of your cell phone or laptop.