This intervention mixed methods study used a quasi-experimental design to investigate the effects of an after-school book club on third-grade boys' reading achievement, attitudes, and preferences. During the 2015-2016 school year, seven third-grade boys from a South Texas elementary school attended an after-school book club in their school library as an alternative to traditional after-school tutoring. The nine-week book club was designed to motivate reading by incorporating the five components of internal reading motivation: perceived control, interest, self-efficacy, involvement, and social collaboration. In addition to reading and discussion, the book club also included adult male guest readers and a service project where participants self-selected books to purchase and add to the school library collection. Quantitative data were collected before and after the intervention in the form of reading assessments and motivation-to-read surveys. These data suggested that the book club intervention had a statistically significant positive impact on the participants' overall reading achievement. Qualitative findings gathered through voice-recorded interviews and video-recorded book-club meetings revealed positive changes in the participants' attitudes toward reading and reading preferences. Additional qualitative findings support prior research studies that suggest a social environment and collaboration can contribute positively to reading motivation. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]