Every once in a while, I receive messages inquiring of the format of the ebooks I have available. So here is my common reply- these ebooks on list are generally in Adobe Reader or .pdf format. (I do have a few ones in .html format, but then, those are easily convertible to pdf or notepad .txt)
Then the next question usually will be, can you have them sent to me in .epub format for my pc tablets? And to this, I would apologize due to my busy life's time constraint. But the good news is, you can convert the pdf file/s yourself by getting hold of the available software online.
So here, let me direct you to a few :
PDF to Epub Converter Download from CNET, which, according to experience is a safe dl site.
I hope that one day I can also try what format works for each pc tablet and what doesn't when I soon win that Kindle Wireless Reading Device, fingers crossed :)