<![CDATA[The development of interactive digital learning media has become an essential strategy for supporting contextual and student-centered mathematics learning. However, the teaching of similarity concepts is still predominantly conducted using conventional instructional media, resulting in students experiencing difficulties in understanding mathematical concepts and applying them to real-life situations. This study aimed to describe the design characteristics and features of an interactive e-book developed using Kotobee Author, explain the integration of the Problem-Based Learning (PBL) syntax into the e-book structure and content, and determine the product's feasibility through expert validation. This study employed a Research and Development (R&D) approach using the ADDIE model, focusing on the Analysis, Design, and Development (ADD) stages. Data were collected through classroom observations, interviews, and expert validation questionnaires involving media and subject-matter experts. The data were analyzed using descriptive quantitative analysis based on percentage scores. The results indicated that the developed interactive e-book features systematically organized learning materials, multimedia content, instructional videos, interactive quizzes, automatic feedback, and user-friendly navigation that can be accessed across various digital devices. Furthermore, the Problem-Based Learning syntax was systematically integrated into the e-book through the stages of problem orientation, organizing learning activities, investigation, presentation of solutions, and evaluation. The expert validation results demonstrated that the e-book achieved a validity score of 93.33% from the media expert and 85.45% from the subject-matter expert, with an overall average of 89.39%, indicating a highly valid category. Therefore, the interactive e-book developed using Kotobee Author and oriented toward Problem-Based Learning is considered feasible for mathematics learning on the topic of similarity. ABSTRAK Pengembangan media pembelajaran digital yang interaktif menjadi salah satu upaya untuk mendukung pembelajaran matematika yang lebih kontekstual dan berpusat pada peserta didik. Namun, pembelajaran materi kesebangunan masih didominasi penggunaan media konvensional sehingga peserta didik mengalami kesulitan dalam memahami konsep dan menghubungkannya dengan permasalahan nyata. Penelitian ini bertujuan untuk mendeskripsikan karakteristik desain dan fitur e-book interaktif berbasis Kotobee Author, menjelaskan integrasi sintaks Problem-Based Learning (PBL) ke dalam struktur dan konten e-book, serta mengetahui kelayakan produk berdasarkan hasil validasi ahli. Penelitian ini merupakan penelitian dan pengembangan (Research and Development) dengan model ADDIE yang difokuskan pada tahap Analysis, Design, dan Development (ADD). Data dikumpulkan melalui observasi, wawancara, serta lembar validasi ahli media dan ahli materi, kemudian dianalisis menggunakan analisis deskriptif kuantitatif dalam bentuk persentase. Hasil penelitian menunjukkan bahwa e-book interaktif memiliki karakteristik berupa penyajian materi yang sistematis, dilengkapi fitur multimedia, video pembelajaran, kuis interaktif, umpan balik otomatis, serta navigasi yang mudah digunakan pada berbagai perangkat digital. Sintaks Problem-Based Learning diintegrasikan secara sistematis melalui tahapan orientasi masalah, pengorganisasian belajar, penyelidikan, penyajian hasil, dan evaluasi. Hasil validasi menunjukkan bahwa e-book memperoleh persentase sebesar 93,33% dari ahli media dan 85,45% dari ahli materi dengan rata-rata 89,39%, sehingga termasuk dalam kategori sangat valid. Dengan demikian, e-book interaktif berbasis Kotobee Author berorientasi Problem-Based Learning dinyatakan layak digunakan sebagai media pembelajaran pada materi kesebangunan. ]]>
