If you want to participate in kernel development, there's really no
substitute for reading the code. Any book on the subject would
necessarily be somewhat out of date and set a general conceptual level.
There are some references that might provide good background (e.g.
"Kernel Hackers Guide") -- check the sites with the Linux Documentation
Project material. But you really need to read the source.
With regards to questions, it's not that easy to get answers, but it
depends on the type of question you ask. If you ask something that could
readily be answered by reading the source, it will probably be ignored,
as many people here are busy and it appears that you maybe didn't really
need to know the answer, since you didn't bother to read the source.
OTOH, if you've studied some difficult area in depth and ask a question
that other people have been wrestling with as well, you may get a
detailed answer.
Regards,
Bill