This book’s aim is to improve the integration of Cognitive Information Processing (CIP) theory, research, and practice, leading to more cost-effective career interventions that help persons to make informed and careful career decisions over a lifetime. The starting point for the book’s content was the 2004 Sampson, Reardon, Peterson, and Lenz book, Career Counseling and Services: A Cognitive Information Processing Approach, which itself was a revision of the material in the 1991 Peterson, Sampson, & Reardon book, Career Development and Services: A Cognitive Approach. We had four goals for this 2023 book. Our first goal was to update the theory, research, and practice of CIP theory from 2004 through the end of 2022. Our second goal was to expand the authors to better reflect the diverse community of practice that has emerged for CIP theory during those eighteen years. Our third goal was to remove cost as a potential barrier to disseminating knowledge about CIP theory by making the book accessible as an open access publication through Florida State Open Publishing. Finally, our fourth goal was to disseminate the book via open-source software available in libraries which can be used to make periodic book content updates more feasible. This book is organized into six sections. The first section (Introduction – Chapter 1) presents key elements of the theory necessary for understanding and using the book’s contents. The second section (Theoretical Concepts Guiding Practice and Research – Chapters 2 through 6) examines theoretical elements of CIP (Pyramid, CASVE cycle, and decision-making readiness) and adds a new chapter on RIASEC theory and CIP, as well as a new chapter on diversity aspects of CIP theory. The third section (Strategies for Delivering CIP-Based Career Interventions – Chapters 7 through 11) presents the differentiated service-delivery model, measures of decision-making readiness, the use of career resources (assessment, information, and instruction), a new chapter on mental health, family, and career intervention, and a new chapter on diversity aspects of CIP-based career interventions. The fourth section (Use of CIP Theory in Practice – Chapters 12 through 15) describes the use of CIP-based career interventions in individual cased-managed, brief staff-assisted, and self-help interventions, as well as a new chapter on international applications of CIP theory. The fifth section (Development, Management, and Evaluation of Career Interventions – Chapters 16 through 20) details how CIP theory was developed and continues to evolve on the basis of evaluation, accountability, planning, and policy. The sixth and final section (Future Directions – Chapter 21) presents a new chapter on the potential future evolution of CIP in relation to theoretical constructs, research, practice, and policy. Each chapter has a common organizational schema as follows: (1) Introductory paragraph indicating the chapter’s purpose, outcomes from reading the chapter, and how the chapter is organized, (2) Content organized into sections and subsections with appropriate APA style headings, (3) A summary of key points covered in the chapter to reinforce schemata, (4) Recommended follow-up activities to help readers better understand and apply the content, and (5) Chapter references.