Where to buy non-kindle-format (epub,azw) e-books which look like the printed books?
I have the same problem. For Springer, I usually buy at its website, where you can find the PDF version. For Oxford and Cambridge, when I cannot find a decent Kindle version, I usually buy at ebooks.
However, for ebooks.com:

The number of available titles is limited, and I couldn't find titles that according to the publishers should be available as e-books.
The PDF is DRM-protected, which is an annoyance.