i highly, highly, highly recommend that you read APE by Guy Kawasaki
anyone writing books can strongly benefit from this (the eBook version is actually preferable)
not only does it cover Kindle Direct publishing but it is fabulous for re-framing any old habits for established authors and also a massive help to new authors
we are setup as full-blown publishers with Lightning Source (which was a massive pain) and have our own ISBN numbers (would have been a great time to be living in Canada where those are free) BUT APE changed our perspectives greatly
APE changed my mind on making more of my OpenSim work free (Hax Nuit is free now if you know where to look) and eventually Enclave Harbour will be free
it's an easy read with lots of highly actionable things you (anyone) can do to succeed