National Learning Corporation has been a leading publisher of test-preparation Passbooks® for more than 50 years, with 6,000 titles available across 22 series. The Test Your Knowledge Series asks What Do You Know About? various subjects or areas of personal interest. Offering tests in multiple-choice format, these books provide students with an opportunity to give themselves "final exams" in areas of concentration or study, or as a self-administered pre-test before an important exam. Others can use these books to measure how much they know about a particular field of interest. These are the types of questions used in popular games of knowledge.