I know this is months later, but I haven't been to visit here as much as I probably ought to.
There's a lot of ways to present your ebooks. You actually don't even have to use PDF or HTML or HieBook or MSReader, etc. Some simply sell their Word or WordPerfect document as their eBook.
I, myself, wouldn't do that, much too easy to change your words.
It's my opinion that it's good to offer more than one format if you can. There are reasonably priced compilers that are easy to use to build HTML eBooks that don't need Internet Explorer to run. Those that do need it tend to be more feature rich, but you may not need or care about that. Too, you could just save your Word or WP doc in HTML right from there, and there's your HTML eBook.
There's several free PDF creators out there. Of which, I've used two. Can't recall which ones now, it was a while ago. All I remember is that the results were not salable. Another I tried was PDF602 or something like that. 602something for sure. Not good at the time. And I paid for that program. They may have improved it by now, but I haven't kept up with them much.
What are you using for a word processor? If you're using a recent version of either Word or WordPerfect, there's a PDF creator built right into the programs. Click print, click the drop down menu, and see if it's listed there along with your printer. Or go to Control Panel, click printers, and check for it there. If it's not and you have Word 2002 or 2003, or WordPerfect 10 or highter, (not sure about 9) slip your disk into the CD drive and do a custom install. To use it, all you have to do is choose it as your printer, name your file, and click save. Your file will compile right before your eyes. Then bring it up in your Adobe Reader to see how it came out.
I've found the quality of the PDF in these two programs to be very good. I can't see much of a difference in those than in the ones I've done with Adobe Acrobat 5.0. I usually just create the PDF in whichever word processing program I'm using at the time, and then use Acrobat to clean it up. I know Acrobat is pricey, I got my copy as a gift. But eBay and Yahoo Auctions have much cheaper prices for it. I'm glad to have a copy, it does make it easier to produce a decent looking file. You can't modify anything from the Reader.
Now, I'm a fiction author, and as such, prefer to do my stuff in HTML. From feedback from readers on eBook elists, HTML is, apparently, more PDA friendly than PDF. I've seen a lot of ranting against PDFs lately. But, nevertheless, these are the two main formats, and I try to offer both. When I can master the mysteries of compiling a decent eBook in for the Hiebook and the MSReader, I'll also offer those.
Hope some of this is helpful to you!