OER Knowledge CloudBook ChapterYuen, Kin SunLi, Kam CheongWong, Billy Tak MingLi, Kam CheongYuen, Kin SunTwelve open textbooks for the local school curriculum – the first set ever developed in Hong Kong – were completed in 2015. During the development process, formative feedback was gathered from primary and secondary school teachers and students who tried out some of the draft versions of the units in the textbooks developed for the project. The evaluation was carried out with the aim of improving the open textbooks being produced. This paper reports the results of the formative evaluation which involved two questionnaires, one for the teachers and the other for the students.20182018/03Springer, Singapore163-175Hong Kong10.1007/978-981-10-7995-5_15978-981-10-7995-5yesOpen Educational Resourcesopen licenceopen textbookstextbook evaluationSingapore, Hong Kong, Asia