Recently I was interested how networks work and everywhere I found recommendations to read TCP/IP Illustrated by Kevin R. Fall and W. Richard Stevens. And it’s an educative book, which explains networks even on a physical level. Almost every chapter also contains information about possible problems and vulnerabilities, which is nice and interesting.
Although reading about the same stuff twice is kind of boring, almost everything is explained for IPv4 and IPv6. And not so small part of the books looks like a reference of packets layout and headers.
But I guess it’s nice to have at least a basic knowledge about networks and this book is more than enough.