Sorry if it's dated. I had this at college (a long long time ago): https://www.amazon.com/File-Structures-2nd-Michael-Folk/dp/0201557134 https://www.amazon.com

Sorry if it's dated. I had this at college (a long long time ago): https://www.amazon.com/File-Structures-2nd-Michael-Folk/dp/0201557134 https://www.amazon.com/File-Structures-2nd-Michael-Folk/dp/0... It was very good, describing b-trees and its variants.