[brendangregg]

Thanks for getting the BPF book. Further references for BPF bits would be the kernel docs (Documentation/bpf), kernel source (kernel/bpf, include/.../bpf), the self tests (tools/testing/selftests/bpf), Cilium's docs (https://docs.cilium.io/en/stable/bpf/), and if all else fails, mailing lists like iovisor-dev.

It sounds like there should be a deep book on BPF internals (written by maintainers Alexei & Daniel), but it would be a tough sell: you really do need the maintainers to author it or be heavily involved to do it well, and it's a lot of work for a changing target, and without a large audience (lots of people will use BPF, but few will code it at that level. I'd guess 100 world-wide. Not a great case for a book!) Compare it to my BPF perf tools book: big audience (end users: developers, SREs, perf engineers, etc), and has a long shelf life (the tools are done, and work, and should keep working).