Sadly, I don't have a solid book recommendation about the early Internet. But, my favorite Internet history book of all time is "IPng: Internet Protocol Next G

Sadly, I don't have a solid book recommendation about the early Internet. But, my favorite Internet history book of all time is "IPng: Internet Protocol Next Generation" edited by Scott O. Bradner and Allison Mankin. It's about the development of what would become IPv6, and each chapter is written by a different engineer who was involved in the process. Some chapters were written for the book, and some chapters were publications/reports from the process.