This study highlights trends and features of E-books and their versatility of this tool in elementary educational settings. There has been little quantitative research employed to examine teachers' reasons for using or not using E-books. The purpose of this study was to examine elementary school mathematics and science teachers' reasons for using or not using E-books and to assess how the use of E-books relates to TPACK among Taiwanese teachers. The survey was developed based on an overview of discussions from prior research related to the benefits and drawbacks of using E-books. The results show the percentages for four reasons for using E-books were high, and low for four reasons for not using E-books. The teachers' perceptions of E-books' usefulness and ability to increase motivation and interaction were significantly different according to gender and the perceptions of E-books' ability to increase interaction were significantly different according to teaching experience. Elementary science teachers demonstrated significantly higher TPACK than elementary mathematics teachers. There was no significant difference found in TPACK according to gender, except for in teachers' technological knowledge. Teachers who had more years of teaching experience demonstrated significantly higher TPACK than the teachers who had fewer years of teaching experience. The results of this study can provide researchers, policy makers, and school administrators with a better understanding of elementary school teachers' perspectives. (Contains 8 tables.)