Simplify the following text for a Grade 11 native English-speaking person.
Original: He conducted more than 2,500 case studies over a period of 40 years and published twelve books , including Twenty Cases Suggestive of Reincarnation and Where Reincarnation and Biology Intersect .
Simplified: He did more than 2,500 interviews over a period of 40 years and wrote twelve books , including Twenty Cases Suggestive of Reincarnation .